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/templates/dashboard.html

@@ -24,8 +24,38 @@
     <div class="stat-value">{{ stats.groupings | length }}</div>
     <div class="stat-label">Distinct groupings</div>
   </div>
+  <div class="stat-card">
+    <div class="stat-value">{{ total_size_human }}</div>
+    <div class="stat-label">Approx. library size</div>
+  </div>
 </div>
 
+<h2>File formats</h2>
+{% if stats.formats %}
+<ul class="chip-list">
+  {% for f in stats.formats %}
+  <li>{{ f.format }} <span class="muted">&times; {{ f.count }}</span></li>
+  {% endfor %}
+</ul>
+{% else %}
+<p class="muted">No format data yet.</p>
+{% endif %}
+
+<h2>Credential status</h2>
+<ul class="chip-list">
+  {% for a in auth_states %}
+  <li>
+    {% if a.configured %}<span class="badge badge-success">set</span>{% else %}<span class="badge badge-muted">unset</span>{% endif %}
+    {{ a.scope }}
+    {% if a.days_left is defined %}
+      {% if a.days_left < 14 %}<span class="badge badge-warning">{{ a.days_left }}d left</span>
+      {% else %}<span class="muted">({{ a.days_left }}d left)</span>{% endif %}
+    {% endif %}
+  </li>
+  {% endfor %}
+</ul>
+<p><a href="/settings/credentials">Manage credentials &rarr;</a></p>
+
 <h2>Recent job runs</h2>
 <div class="table-wrap scroll">
   <table>