fix(logs): keep polling reads and a channel-less account out of the warnings

The reads the frontend polls (unread counts, /api/me, the download index,
sync status, subtitle progress) are logged at DEBUG: at INFO they were ~95%
of the stored log on prod. A scheduler job failure and a playlist sync
failure carry event codes, and a Google account without a YouTube channel
has an empty playlist list instead of a warning every six hours.

backend/app/logs.py

@@ -644,6 +644,27 @@ _REQUEST_ID_RE = re.compile(r"^[A-Za-z0-9._-]{8,64}$")
 # — this lowers the floor, it does not hide.
 _QUIET_PREFIXES = ("/healthz", "/assets/", "/static/", "/api/admin/logs")
 
+# The reads the frontend POLLS (a `useLiveQuery`, the `me` heartbeat, the sync status, the subtitle
+# progress), by route template, GET only — logged at DEBUG like the prefixes above. One open tab asked
+# for the two unread counts, `/api/me` and the download index every 30 s, and at INFO those were ~95%
+# of the stored log (measured on prod 2026-09-19): 11k lines a day per tab burying every line someone
+# caused. The same route answered with a failure still logs at WARNING/ERROR.
+_POLLED_ROUTES = frozenset(
+    {
+        "/api/me",
+        "/api/me/notifications/unread_count",
+        "/api/messages/unread_count",
+        "/api/downloads",
+        "/api/downloads/index",
+        "/api/downloads/usage",
+        "/api/sync/my-status",
+        "/api/admin/scheduler",
+        "/api/admin/downloads",
+        "/api/admin/downloads/storage",
+        "/api/plex/subtitle/{rating_key}/{sub_ord}/status",
+    }
+)
+
 # Not `siftlode.logs`: this is the replacement for uvicorn's ACCESS log, and `siftlode.http` is
 # what an operator pins a level on when they want request lines and nothing else. The module it
 # happens to live in is not what the name is about.
@@ -689,7 +710,9 @@ async def log_requests(request, call_next):
         raise
     duration_ms = round((time.perf_counter() - started) * 1000, 1)
     status = response.status_code
-    quiet = request.url.path.startswith(_QUIET_PREFIXES)
+    quiet = request.url.path.startswith(_QUIET_PREFIXES) or (
+        request.method == "GET" and _route_template(request) in _POLLED_ROUTES
+    )
     if status >= 500:
         level = logging.ERROR
     elif status >= 400: