fix(logs): rule on every swallowed exception in the backend

114 exception handlers neither logged nor re-raised. The defect was never that
they are silent — plenty of them should be — it is that their silence said
nothing, so nobody could tell a decision from an oversight. Each one has now been
read. 44 got a line; the other 70 carry `# silent-ok: <why>`.

What the silent ones had been hiding, in the cases that got a line:
- A failed ffprobe sent every HDR file down the 8-bit pipeline, so playback
  degraded to a software transcode with nothing saying why; a failed audio probe
  collapsed a multi-audio file to one track and the player showed no language
  picker; a failed first-PTS probe left subtitles seconds out of sync.
- A subtitle sidecar that existed but would not parse made a PARTIAL track read as
  complete, permanently — the viewer loses every cue past the cached window.
- An unreadable crop/trim/cut-list in an edit spec was dropped, so the clip came
  out uncropped, untrimmed, or shorter than the one the user built.
- A dropped `max_height` downloaded at best quality against an explicit cap.
- A failed videos.list enrich made every candidate undroppable-from-judgement and
  therefore dropped: a working search rendered as "no results".
- An unusable password hash answered as "wrong password", locking the owner out
  and telling them they mistyped; a rotated TOKEN_ENCRYPTION_KEY turned every
  stored token into "not connected".
- A stored admin setting that would not coerce fell back to the env default while
  the settings page went on showing the saved value.
- A one-off InnerTube config failure pinned the whole process to the hard-coded
  fallback key, and searches return nothing when that goes stale.
- The HLS sweep reported 0 swept — like a clean run — when it could not list its
  own root, leaving every crashed session's segments on disk forever.

Four of them are counted rather than logged per item (dropped cues, dropped cut
list segments, unreclaimed GC files) and reported once per call, because the
alternative is one line per cue over a whole subtitle track.

ruff gains S110 and BLE001. Every blind `except Exception` that remains carries
`# noqa: BLE001 — <why>`, which is the point: catching everything is sometimes
right, and always worth a sentence. plex/sync.py's three best-effort backfill
catches now keep the traceback — a blind catch over a batch that fetches AND
writes could be Plex, the database or our own bug, and `%s` of the exception told
them apart badly. main.py's boot-time log-level read likewise.

logs.event's `code` is positional-only now: `event("x", code=...)` was a TypeError,
and `code` is exactly the word a caller reaches for when the thing that failed has
one of its own.

tests/test_swallowed_exceptions.py is the wider rule ruff cannot see: a handler
that neither logs nor re-raises must say why. Both cases mutation-checked — a
marker removed and a log line removed each fail it, naming the handler.

backend/app/downloads/edit.py

@@ -71,7 +71,13 @@ def normalize_edit_spec(spec: dict | None) -> dict:
     if crop:
         try:
             c = {k: int(round(float(crop[k]))) for k in ("x", "y", "w", "h")}
-        except (KeyError, TypeError, ValueError):
+        except (KeyError, TypeError, ValueError) as exc:
+            # The clip still renders — uncropped. The user asked for a crop, got a whole frame,
+            # and nothing anywhere called it a failure; this line is the only trace there is.
+            log.warning(
+                "the crop in an edit spec could not be read and was dropped",
+                extra=logs.event("edit.spec.crop_dropped", reason=type(exc).__name__),
+            )
             c = None
         if c and c["w"] > 0 and c["h"] > 0 and c["x"] >= 0 and c["y"] >= 0:
             out["crop"] = c
@@ -80,6 +86,7 @@ def normalize_edit_spec(spec: dict | None) -> dict:
     segs = spec.get("segments")
     if isinstance(segs, list) and segs:
         norm: list[dict] = []
+        unreadable = 0
         for s in segs:
             try:
                 st = max(0.0, float((s or {}).get("start_s") or 0.0))
@@ -88,9 +95,18 @@ def normalize_edit_spec(spec: dict | None) -> dict:
                     continue
                 en = float(end_raw)
             except (TypeError, ValueError):
+                # silent-ok: counted, not logged here — one cut-list can drop several, and the
+                # join that comes out is simply shorter than the one the user built. Reported
+                # once after the loop.
+                unreadable += 1
                 continue
             if en > st:
                 norm.append({"start_s": round(st, 3), "end_s": round(en, 3)})
+        if unreadable:
+            log.warning(
+                "some segments of a cut list could not be read and were dropped",
+                extra=logs.event("edit.spec.segments_dropped", dropped=unreadable, kept=len(norm)),
+            )
         norm.sort(key=lambda x: x["start_s"])
         # SEC-13: an accurate join builds one ffmpeg `filter_complex` with two filters per segment,
         # so an unbounded list becomes an unbounded command line and an ffmpeg that never finishes.
@@ -114,7 +130,13 @@ def normalize_edit_spec(spec: dict | None) -> dict:
             start = max(0.0, float(trim.get("start_s") or 0.0))
             end_raw = trim.get("end_s")
             end = float(end_raw) if end_raw is not None else None
-        except (TypeError, ValueError):
+        except (TypeError, ValueError) as exc:
+            # Either a 400 the user cannot act on, or — beside a crop — a full-length clip where
+            # they asked for a cut. Both are worth one line saying the spec was the problem.
+            log.warning(
+                "the trim in an edit spec could not be read and was dropped",
+                extra=logs.event("edit.spec.trim_dropped", reason=type(exc).__name__),
+            )
             start, end = 0.0, None
         t: dict = {"start_s": round(start, 3)}
         if end is not None and end > start:
@@ -306,11 +328,14 @@ def _parse_out_time(line: str) -> float | None:
     if line.startswith("out_time_us="):
         try:
             return int(line.split("=", 1)[1]) / 1_000_000
+        # silent-ok: one line of ffmpeg's `-progress` stream, several per second. None means "this
+        # line carried no usable time", which the caller already treats as "no progress yet".
         except ValueError:
             return None
     if line.startswith("out_time_ms="):  # (some builds mislabel this as microseconds)
         try:
             return int(line.split("=", 1)[1]) / 1_000_000
+        # silent-ok: as above, the other spelling of the same line.
         except ValueError:
             return None
     return None
@@ -329,7 +354,9 @@ def _pump(stream, sink: "queue.Queue[str | None]") -> None:
     try:
         for line in stream:
             sink.put(line)
-    except (ValueError, OSError):  # pipe closed under us by the kill path
+    # silent-ok: the pipe was closed under us by our OWN kill path — the expected end of a
+    # cancelled or timed-out run, and the code that did the killing is the code that reports it.
+    except (ValueError, OSError):
         pass
     finally:
         sink.put(None)
@@ -347,6 +374,8 @@ def _drain_tail(stream, sink: list[str]) -> None:
             sink.append(line)
             if len(sink) > 200:
                 del sink[:100]
+    # silent-ok: same closed pipe as `_pump` above, and the tail collected so far is still handed
+    # to whoever reports the failure.
     except (ValueError, OSError):
         pass
 
@@ -362,6 +391,8 @@ def escalate_kill(proc: subprocess.Popen, terminate, kill, grace_s: float, label
     try:
         proc.wait(timeout=grace_s)
         return
+    # silent-ok: the escalation below IS the handling of this timeout, and surviving THAT is what
+    # the line under the second wait reports.
     except subprocess.TimeoutExpired:
         pass
     kill()
@@ -406,6 +437,8 @@ def run_ffmpeg(
         while True:
             try:
                 line = lines.get(timeout=1.0)
+            # silent-ok: not a failure — the one-second timeout is how this loop gets a turn to
+            # poll for cancellation while ffmpeg is quiet.
             except queue.Empty:
                 line = ""
             if line is None:  # stdout hit EOF — ffmpeg is done (or dying)
@@ -473,7 +506,13 @@ def run_ffprobe_json(
     try:
         out = subprocess.run(args, capture_output=True, text=True, timeout=30, check=True).stdout
         return json.loads(out)
-    except (subprocess.TimeoutExpired, subprocess.CalledProcessError, OSError, ValueError):
+    except (subprocess.TimeoutExpired, subprocess.CalledProcessError, OSError, ValueError) as exc:
+        # None makes every field it would have filled read as absent, and a file with no streams
+        # and no duration is indistinguishable here from one that is not media at all.
+        log.warning(
+            "ffprobe could not read a file",
+            extra=logs.event("media.ffprobe_failed", reason=type(exc).__name__),
+        )
         return None
 
 
@@ -527,7 +566,13 @@ def probe_duration(path: Path) -> int:
             check=True,
         ).stdout.strip()
         return int(float(out)) if out else 0
-    except (subprocess.TimeoutExpired, subprocess.CalledProcessError, OSError, ValueError):
+    except (subprocess.TimeoutExpired, subprocess.CalledProcessError, OSError, ValueError) as exc:
+        # Zero is the denominator of the re-encode progress bar, so a failed probe leaves the user
+        # watching a bar that never moves rather than a job that says it went wrong.
+        log.info(
+            "the duration probe failed; progress for this job has no total",
+            extra=logs.event("media.duration_probe_failed", reason=type(exc).__name__),
+        )
         return 0
 
 
@@ -672,6 +717,8 @@ def _run_ffmpeg_best_effort(cmd: list[str], timeout_s: int) -> Exception | None:
     try:
         subprocess.run(cmd, capture_output=True, timeout=timeout_s, check=True)
         return None
+    # silent-ok: the exception is the RETURN VALUE. This helper exists so the three callers share
+    # one run/timeout policy, and each logs the failure with the context only it has.
     except (subprocess.TimeoutExpired, subprocess.CalledProcessError, OSError) as exc:
         return exc
 
@@ -681,6 +728,8 @@ def _is_jpeg(path: Path) -> bool:
     try:
         with path.open("rb") as f:
             return f.read(3) == b"\xff\xd8\xff"
+    # silent-ok: False only means "do not copy this straight through" — the caller then goes the
+    # ffmpeg route, which opens the same file and reports it properly if it really is unreadable.
     except OSError:
         return False