Dashboard detail, library filtering/pagination, simplified playlist times,

job descriptions

Dashboard: format breakdown (FLAC/MP3/etc. counts), approximate library
size (bitrate*length/8, same approximation `beet stats` itself uses --
verified to match its "100.5 GiB" output exactly against the real
library), and a credential auth-state summary per scope (configured y/n
plus, for Bandcamp, cookie expiry parsed locally from the stored cookie
jar -- deliberately not a live network probe like pipeline-status.sh's
Qobuz check, since this renders on every dashboard load).

Library: was one unfiltered page dumping all 4072 tracks. Added search
(artist/title/album), playlist and format filter dropdowns, and real
SQL-level pagination (LIMIT/OFFSET, not fetch-everything-then-slice).
beets_service gained count_items()/distinct_formats() to support this.

Playlists: cron_expr is still the stored/scheduled representation, but the
UI now shows and edits a plain daily time picker instead of raw cron
syntax -- every playlist schedule today is a simple daily HH:MM anyway.
playlist_service.cron_to_time()/time_to_cron() convert at the router
boundary; verified round-trip against all real playlist cron values.

Jobs: each maintenance job now shows a short one-line description of what
it actually does (MAINTENANCE_JOB_DESCRIPTIONS), and "next run" is
formatted consistently with playlists' time style (HH:MM, with a day
qualifier for non-today runs -- maintenance jobs can be weekly/monthly,
unlike playlists' plain daily schedule).

Verified end-to-end against the real production data (4072 tracks, 100.5
GiB, real credentials): stats/format-breakdown/search/pagination all
correct, all 7 credential scopes report configured with Bandcamp's real
cookie expiry (325 days), and a full authenticated page-render sweep
(dashboard, library with every filter combination, playlist detail,
jobs) all returned 200 with no template errors.

app/services/playlist_service.py

@@ -8,6 +8,39 @@ from sqlalchemy.orm import Session
 from app.models import Playlist
 from app.settings import settings
 
+
+def cron_to_time(cron_expr: str | None) -> str:
+    """'30 1 * * *' -> '01:30'. Every playlist schedule today is a simple
+    daily HH:MM (no day-of-week/day-of-month complexity -- that's only used
+    by a couple of maintenance jobs), so the UI can offer a plain time
+    picker instead of raw cron syntax. Returns '' for anything else
+    (unscheduled, or a cron expression more complex than daily-at-HH:MM)."""
+    if not cron_expr:
+        return ""
+    parts = cron_expr.split()
+    if len(parts) == 5 and parts[2] == "*" and parts[3] == "*" and parts[4] == "*":
+        try:
+            hour, minute = int(parts[1]), int(parts[0])
+            if 0 <= hour < 24 and 0 <= minute < 60:
+                return f"{hour:02d}:{minute:02d}"
+        except ValueError:
+            pass
+    return ""
+
+
+def time_to_cron(time_str: str | None) -> str | None:
+    """'01:30' -> '30 1 * * *'. Empty/invalid input means unscheduled."""
+    if not time_str:
+        return None
+    try:
+        hour_str, minute_str = time_str.split(":")
+        hour, minute = int(hour_str), int(minute_str)
+    except ValueError:
+        return None
+    if not (0 <= hour < 24 and 0 <= minute < 60):
+        return None
+    return f"{minute} {hour} * * *"
+
 # The 17-entry array this project is migrating off of (was hardcoded in
 # /opt/sldl/configs/regen.sh). Used once by seed_legacy() during Stage 1/2
 # of the migration; the DB is the source of truth from then on. cron_expr