feat: hide-from-views flag on folders

Adds a per-folder "hide from views" toggle so noisy subtrees
(screenshots, WhatsApp dumps, work archives) can be excluded from
cross-cutting views without losing indexing. Photos under a hidden
folder are still scanned, thumbnailed, embedded, OCR'd, face-
extracted — they just stop appearing in All Photos, Rated, Colors,
Map, Tags, People, Search, Duplicates, and the sidebar counts.
Navigating directly into the folder still shows every photo.

Schema (migration 0007_folder_hidden):
- folders.is_hidden   user-set toggle, default false
- photos.is_hidden    denormalized effective flag (true iff any
                      ancestor folder is hidden), indexed so cross-
                      cutting queries stay on the existing planner
                      paths

The denorm is maintained by two paths:
- The scanner walks the ancestry chain on insert, with a per-scan
  memoized cache so each folder is resolved once per scan.
- POST /api/v1/folders/{id}/hide flips folders.is_hidden and runs a
  WITH RECURSIVE CTE to recompute every folder's effective state in
  one query, then bulk-updates photos WHERE IS DISTINCT FROM. Runs
  in ~10 ms on a 13k-photo library.

Filters added (cross-cutting queries):
- /library/stats — every sidebar badge via a shared `visible` filter
- /photos (list) — only when neither folder_id nor heap_id is set;
  folder browse and heap browse always show everything
- /photos/map
- /library/duplicates/groups
- /folders/tree photo_count subquery
- /tags count_subq (drives Tags + People sidebar counts)
- services/duplicates.regroup_duplicates (so hidden dupes never
  contaminate the Duplicates view)
- services/search.hybrid_search — both semantic (pgvector) and FTS
  legs join photos so rankings don't include hidden results

Intentionally NOT filtered:
- /photos?folder_id=X and /photos?heap_id=X (user-intentional browse)
- /library/maintenance/pipeline-stats (tracks real worker state)
- cleanup service (disk-level ops, not views)

Frontend:
- sourceFolders.setHidden(id, hidden) API client method
- FolderTreeNode.is_hidden carried through the tree into TreeItem
- LeftSidebar kebab menu: "Hide from views" / "Show in views" with a
  mutation that invalidates folders, photos, stats, and tags caches
- Hidden folder rows swap the Folder icon for EyeOff and render the
  label italic/muted so the state is visible at a glance

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

backend/app/models/folders.py

@@ -22,7 +22,7 @@ class SourceRoot(Base):
 
 class Folder(Base):
     __tablename__ = 'folders'
-    
+
     id = Column(String, primary_key=True, default=lambda: str(uuid.uuid4()))
     name = Column(String, nullable=False)
     path = Column(String, unique=True, nullable=False)
@@ -30,7 +30,16 @@ class Folder(Base):
     source_root_id = Column(String, ForeignKey('source_roots.id'))
     photo_count = Column(Integer, default=0)
     last_scanned = Column(DateTime)
-    
+
+    # "Hide from views" — when true, photos in this folder (and every
+    # descendant folder) are excluded from cross-cutting views like
+    # All Photos, Map, Tags, People, Search and the sidebar counts.
+    # Photos are still scanned, thumbnailed and indexed — they just
+    # stop showing up unless the user navigates directly to a folder
+    # inside the hidden subtree. The effective flag is materialized
+    # onto Photo.is_hidden so queries don't have to walk parent_id.
+    is_hidden = Column(Boolean, nullable=False, default=False, server_default='false')
+
     # Relationships
     source_root = relationship("SourceRoot", back_populates="folders")
     photos = relationship("Photo", backref="folder")

backend/app/models/photos.py

@@ -37,6 +37,15 @@ class Photo(Base):
     # a migration; only the Python attribute name reflects the rename.
     is_discarded = Column('is_trashed', Boolean, default=False)
     discarded_at = Column('trashed_at', DateTime)
+
+    # "Hidden from views" — materialized from Folder.is_hidden walking
+    # the ancestry chain. True iff any ancestor folder (including the
+    # photo's direct folder) is hidden. Cross-cutting queries filter
+    # `AND NOT is_hidden`; per-folder browses ignore the flag so the
+    # user can still open a hidden folder and see its contents. The
+    # column is maintained by two places: the scanner sets it on new
+    # rows, and POST /folders/{id}/hide recomputes it on toggle.
+    is_hidden = Column(Boolean, nullable=False, default=False, server_default='false', index=True)
     
     # Thumbnail paths
     thumb_small = Column(String)  # path to 240px thumb