fix(modal): pin Related to rail bottom, floppy-disk download, drop suggestions cap

Right-rail layout fixes (operator-flagged 2026-06-26 — the prior change wasn't
the intended improvement):

- Pin the Related strip to the BOTTOM of the rail: the side becomes a flex
  column with a scrolling main area (meta + provenance + tags + suggestions)
  and a pinned Related footer (capped at 45% of the rail, scrolls past that).
  Related now stays reachable no matter how long Tags/Suggestions run, and
  self-collapses (no footer space) when there's nothing to show.
- Remove the 320px suggestions scroll cap (3fcc4ae) — it was a workaround "so
  Related stays reachable"; pinning Related is the proper fix, so suggestions
  flow in the single main scroll instead of a nested scrollbar.
- Shrink the Download button to a floppy-disk save icon (mdi-content-save); the
  meta (dimensions/size/type) + save action now sit as a compact top block
  (meta left, icon right). Copy link moves into the adjacent kebab menu.

ImageMetaBar is shared with the Explore center pane, so the compact save
control applies there too (parity). Mobile (<=900px) keeps the single body
scroll — no nested scroll, Related flows at the end.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/src/components/modal/ImageMetaBar.vue

@@ -1,7 +1,8 @@
 <template>
   <section v-if="img" class="fc-meta" aria-label="Image details">
-    <!-- #4a: dimensions / size / type — already on the payload, shown nowhere
-         until now. -->
+    <!-- #4a: dimensions / size / type sit as a compact top block alongside a
+         small save action (operator-asked 2026-06-26) — meta on the left, the
+         download control shrunk to a floppy-disk icon on the right. -->
     <dl class="fc-meta__grid">
       <div v-if="img.width && img.height" class="fc-meta__item">
         <dt>Dimensions</dt><dd>{{ img.width }} × {{ img.height }}</dd>
@@ -14,21 +15,27 @@
       </div>
     </dl>
 
-    <!-- #4b: split Download — default Download, chevron → Copy link. Image-to-
-         clipboard is OFF the table on the plain-HTTP origin (rule 95), so the
-         secondary action copies the link TEXT, which works everywhere. -->
-    <v-btn-group divided density="comfortable" variant="tonal" color="accent" rounded="pill">
-      <v-btn prepend-icon="mdi-download" @click="download">Download</v-btn>
+    <!-- #4b: floppy-disk save icon = download; the kebab menu keeps Copy link.
+         Image-to-clipboard is OFF the table on the plain-HTTP origin (rule 95),
+         so the secondary action copies the link TEXT, which works everywhere. -->
+    <div class="fc-meta__actions">
+      <v-btn
+        icon="mdi-content-save" size="small" variant="tonal" color="accent"
+        aria-label="Download image" title="Download" @click="download"
+      />
       <v-menu location="bottom end">
         <template #activator="{ props }">
-          <v-btn v-bind="props" icon="mdi-chevron-down" aria-label="More download options" />
+          <v-btn
+            v-bind="props" icon="mdi-dots-vertical" size="small" variant="text"
+            aria-label="More download options"
+          />
         </template>
         <v-list density="compact">
           <v-list-item prepend-icon="mdi-link-variant" title="Copy link" @click="copyLink" />
-          <v-list-item prepend-icon="mdi-download" title="Download" @click="download" />
+          <v-list-item prepend-icon="mdi-content-save" title="Download" @click="download" />
         </v-list>
       </v-menu>
-    </v-btn-group>
+    </div>
   </section>
 </template>
 
@@ -83,11 +90,16 @@ async function copyLink () {
 <style scoped>
 .fc-meta {
   padding: 14px 16px 0;
-  display: flex; flex-direction: column; gap: 10px;
+  display: flex; align-items: flex-start; gap: 12px;
 }
 .fc-meta__grid {
+  flex: 1 1 auto; min-width: 0;
   display: flex; flex-wrap: wrap; gap: 4px 18px; margin: 0;
 }
+.fc-meta__actions {
+  flex: 0 0 auto;
+  display: flex; align-items: center; gap: 2px;
+}
 .fc-meta__item { display: flex; flex-direction: column; }
 .fc-meta__item dt {
   font-size: 10px; text-transform: uppercase; letter-spacing: 0.06em;