feat(model-manager): generated-photo Gallery + device-routing landing

- Gallery view: grid of generated photos from ComfyUI's output/, full-size
  lightbox, and permanent delete (with confirm). Paginated ("Load more").
- Backend: GET /api/gallery, GET /gallery/file (path-guarded image serve),
  DELETE /api/gallery (path-guarded; clear error on permission denial).
- Mount ./output read-write into model-manager so the gallery can delete.
- Device-routing landing at /start: phones -> ComfyUIMini, desktops ->
  the Gallery; ?force=mobile|desktop overrides. Ports come from the new
  /api/ui-config (COMFYUI_PORT / COMFYUIMINI_PORT env).
- Responsive tweaks so the gallery is usable if opened directly on a phone.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

model-manager/app/static/index.html

@@ -20,6 +20,9 @@
         <button class="nav-item active" data-view="installed">
           <span class="nav-ico">▦</span> Installed Models
         </button>
+        <button class="nav-item" data-view="gallery">
+          <span class="nav-ico">🖼</span> Gallery
+        </button>
         <button class="nav-item" data-view="browse">
           <span class="nav-ico">🔍</span> Browse CivitAI
         </button>
@@ -48,6 +51,23 @@
         </div>
       </section>
 
+      <!-- Gallery (generated photos) -->
+      <section class="view" id="view-gallery">
+        <header class="view-head">
+          <h1>Gallery</h1>
+          <div class="head-actions">
+            <span class="form-msg" id="galleryToast"></span>
+            <button class="btn" id="refreshGallery">Refresh</button>
+          </div>
+        </header>
+        <div id="galleryGrid" class="gallery-grid">
+          <p class="empty">Loading…</p>
+        </div>
+        <div class="browse-more">
+          <button class="btn" id="galleryMore" style="display:none">Load more</button>
+        </div>
+      </section>
+
       <!-- Browse CivitAI -->
       <section class="view" id="view-browse">
         <header class="view-head">
@@ -160,6 +180,20 @@
       </section>
     </main>
   </div>
+
+  <!-- Lightbox for full-size photo viewing -->
+  <div id="lightbox" class="lightbox" hidden>
+    <button class="lb-close" id="lbClose" title="Close">✕</button>
+    <img id="lbImage" alt="" />
+    <div class="lb-bar">
+      <span id="lbName" class="lb-name"></span>
+      <span class="lb-actions">
+        <a id="lbOpen" class="btn" target="_blank" rel="noopener">Open original</a>
+        <button class="btn danger" id="lbDelete">Delete</button>
+      </span>
+    </div>
+  </div>
+
   <script src="/app.js"></script>
 </body>
 </html>