Restructure Settings nav, modernize import page, dedup/genres UX polish

Settings is now one top-nav entry with Credentials and Jobs as sidebar
sub-pages (jobs moved from /jobs to /settings/jobs). Manual import page
replaces the bare file input and free-text filename field with a drag-drop
dropzone and a proper file-picker table. Genres page drops the "force"
checkbox for two explicit buttons (Preview / Fix genres now). Dedup's
"Scan now" runs both the file-naming and acoustic passes together, and the
table labels which pass caught each candidate instead of showing the raw
pass name. .btn-ghost gets a visible border so it reads as a real button
next to Delete/Danger actions instead of looking unaligned. Job names
throughout the UI are now human-readable instead of raw job_key strings.

Also includes the fpcalc exit-code fix from earlier (fingerprint index
was discarding valid fingerprints on files with a benign decode warning).

app/templates/playlists/detail.html

@@ -9,7 +9,7 @@
     <p class="subtitle muted"><a href="{{ playlist.spotify_url }}">{{ playlist.spotify_url }}</a></p>
   </div>
   <div class="actions">
-    <form method="post" action="/jobs/playlist:{{ playlist.name }}/run" class="inline">
+    <form method="post" action="/settings/jobs/playlist:{{ playlist.name }}/run" class="inline">
       <button type="submit" class="btn btn-primary">Run now</button>
     </form>
   </div>