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/genres/index.html

@@ -9,10 +9,15 @@
 </div>
 
 <div class="panel" style="max-width:560px;">
-  <form method="post" action="/genres/scan">
-    <label class="checkbox-field"><input type="checkbox" name="force" value="true"> Force (overwrite existing genres)</label>
-    <button type="submit" class="btn btn-primary">Preview now (dry run)</button>
-  </form>
+  <p class="muted" style="margin-top:0;">Preview shows what would change, including overwriting existing genres. Fix writes those changes for real.</p>
+  <div class="btn-row">
+    <form method="post" action="/genres/scan" class="inline">
+      <button type="submit" class="btn btn-ghost">Preview changes</button>
+    </form>
+    <form method="post" action="/genres/apply" class="inline">
+      <button type="submit" class="btn btn-primary">Fix genres now</button>
+    </form>
+  </div>
 </div>
 
 <h2>Last run</h2>