feat: share heaps and folders with other users, fix auth and vision pipeline

Sharing:
- New HeapShare and FolderShare models with read/write permissions
- Sharing API router (CRUD for heap and folder shares)
- Heap endpoints accept shared access (photo_ids, add/remove with write)
- Photo list drops user_id filter in shared context, adds owner_username
- Media serving (thumb/original/proxy) falls back to share check on 404
- ShareDialog component for managing shares from kebab menus
- HeapsPanel shows "Shared with me" section for shared heaps
- LeftSidebar shows "Shared with me" section for shared folders
- Owner badge on PhotoThumbnail for photos from other users

Auth:
- Access token default bumped to 1 year, refresh to 10 years
- Refresh token persisted in localStorage (survives page reload)
- Timer-based refresh replaced with 401 axios interceptor

Vision pipeline fixes:
- Bootstrap sets Redis ready key even on partial export failure
- Export functions run conditionally (only for actually missing models)
- _load_thumb handles multi-user path (/data/thumbs/{user_id}/{photo_id}/)
- can_access_photo_via_share uses single subquery instead of N+1 loop

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

frontend/src/components/timeline/PhotoThumbnail.tsx

@@ -7,6 +7,7 @@ import {
   Check,
   Copy,
   AlertTriangle,
+  Users,
 } from 'lucide-react'
 import clsx from 'clsx'
 import { photos as photosApi } from '../../services/api'
@@ -328,6 +329,24 @@ export function PhotoThumbnail({
         </div>
       )}
 
+      {/* TL offset — owner badge for shared photos. Sits below the
+       *  selection check so both can show simultaneously. */}
+      {photo.owner_username && (
+        <div
+          className={clsx(
+            'absolute left-1',
+            isSelected ? 'top-7' : 'top-1',
+            THUMB_BADGE_BASE,
+            THUMB_BADGE_NEUTRAL,
+            'max-w-[90px]'
+          )}
+          title={`Photo owned by ${photo.owner_username}`}
+        >
+          <Users className={THUMB_BADGE_ICON} strokeWidth={2.5} />
+          <span className="truncate">{photo.owner_username}</span>
+        </div>
+      )}
+
       {/* BL — color label + rating. Color comes first (left of rating)
        *  so the swatch reads as a "category dot" prefixing the stars. */}
       {(photo.color_label || photo.rating > 0) && (