style: apply ruff format across backend + scripts (line-length 100)

Mechanical, whole-tree `ruff format` pass — no behaviour change. Recorded in
.git-blame-ignore-revs (next commit) so git blame skips it.

backend/app/plex/subtitles.py

@@ -26,9 +26,7 @@ BITMAP_SUBS = {
 def srt_to_vtt(text: str) -> str:
     """Minimal SubRip→WebVTT: add the header and switch the ms separator (`,`→`.`). SRT cue-index
     lines are valid in WebVTT, so they're left as-is."""
-    body = re.sub(
-        r"(\d\d:\d\d:\d\d),(\d\d\d)", r"\1.\2", text.replace("\r\n", "\n").lstrip("")
-    )
+    body = re.sub(r"(\d\d:\d\d:\d\d),(\d\d\d)", r"\1.\2", text.replace("\r\n", "\n").lstrip(""))
     return "WEBVTT\n\n" + body.strip() + "\n"
 
 
@@ -114,8 +112,7 @@ def ffmpeg_to_vtt(src: str, sub_ord: int | None) -> str:
     r = subprocess.run(cmd, capture_output=True)
     if r.returncode != 0 or not r.stdout:
         raise PlexError(
-            (r.stderr or b"").decode("utf-8", "replace")[:200]
-            or "ffmpeg subtitle convert failed"
+            (r.stderr or b"").decode("utf-8", "replace")[:200] or "ffmpeg subtitle convert failed"
         )
     return r.stdout.decode("utf-8", "replace")