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>

backend/alembic/versions/0011_sharing.py

@@ -0,0 +1,54 @@
+"""Add sharing tables for heaps and folders
+
+Revision ID: 0011_sharing
+Revises: 0010_embeddings_768d
+Create Date: 2026-04-13
+
+Adds heap_shares and folder_shares tables so users can share
+heaps and folders with other users (read or read+write).
+"""
+from typing import Sequence, Union
+
+from alembic import op
+import sqlalchemy as sa
+
+revision: str = "0011_sharing"
+down_revision: Union[str, None] = "0010_embeddings_768d"
+branch_labels: Union[str, Sequence[str], None] = None
+depends_on: Union[str, Sequence[str], None] = None
+
+
+def upgrade() -> None:
+    op.execute("""
+        CREATE TABLE IF NOT EXISTS heap_shares (
+            id VARCHAR NOT NULL PRIMARY KEY,
+            heap_id VARCHAR NOT NULL REFERENCES heaps(id) ON DELETE CASCADE,
+            owner_id VARCHAR NOT NULL REFERENCES users(id),
+            shared_with_id VARCHAR NOT NULL REFERENCES users(id),
+            permission VARCHAR NOT NULL DEFAULT 'read',
+            created_at TIMESTAMP DEFAULT now(),
+            CONSTRAINT uq_heap_share UNIQUE (heap_id, shared_with_id)
+        )
+    """)
+    op.execute("CREATE INDEX IF NOT EXISTS ix_heap_shares_shared_with ON heap_shares(shared_with_id)")
+    op.execute("CREATE INDEX IF NOT EXISTS ix_heap_shares_heap_id ON heap_shares(heap_id)")
+
+    op.execute("""
+        CREATE TABLE IF NOT EXISTS folder_shares (
+            id VARCHAR NOT NULL PRIMARY KEY,
+            folder_id VARCHAR NOT NULL,
+            folder_type VARCHAR NOT NULL DEFAULT 'folder',
+            owner_id VARCHAR NOT NULL REFERENCES users(id),
+            shared_with_id VARCHAR NOT NULL REFERENCES users(id),
+            permission VARCHAR NOT NULL DEFAULT 'read',
+            created_at TIMESTAMP DEFAULT now(),
+            CONSTRAINT uq_folder_share UNIQUE (folder_id, shared_with_id)
+        )
+    """)
+    op.execute("CREATE INDEX IF NOT EXISTS ix_folder_shares_shared_with ON folder_shares(shared_with_id)")
+    op.execute("CREATE INDEX IF NOT EXISTS ix_folder_shares_folder_id ON folder_shares(folder_id)")
+
+
+def downgrade() -> None:
+    op.execute("DROP TABLE IF EXISTS folder_shares")
+    op.execute("DROP TABLE IF EXISTS heap_shares")