feat(web): missing-subtitles queue alongside no-pt-source

A third lane in the attention queues view: one row per movie or
series with a gap chip per language and why (#186's reasons, plus a
sync alass flagged). Reuses the existing deck-group markup and
missingChipLabel wording so it reads like its two siblings; each
row opens the title's own page, where the #203 fetch/translate
panel already carries the resolving actions.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

web/index.html

@@ -199,6 +199,19 @@
         </p>
         <ul class="deck-rows" id="rows-decision"></ul>
       </section>
+
+      <section class="deck-group" id="queue-subtitles" hidden aria-labelledby="label-subtitles">
+        <header class="deck-head">
+          <h3 class="deck-label" id="label-subtitles">missing subtitles</h3>
+          <span class="deck-count readout" id="count-subtitles"></span>
+        </header>
+        <p class="queue-note readout dim">
+          a wanted language with no subtitle, and why — no candidate, a translation or provider
+          failure, the daily budget, or a sync `alass` flagged. open the title to search,
+          translate or retry by hand.
+        </p>
+        <ul class="deck-rows" id="rows-subtitles"></ul>
+      </section>
     </main>
 
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