M6 1902a: richer facet query + saved-filters storage (backend)

GET /api/notes gains combinable, AND-ed facets alongside the existing
filter/date/sort: multiple ?label= (notes with ALL), ?color, ?kind,
?has_reminder, ?has_attachment, and ?q (full-text over title+body, ranked)
— so the facet bar's text box searches, not just filters. All optional;
invalid color/kind → 400.

saved_filters table (migration 0021) + /api/saved-filters CRUD (list /
create / rename+repoint / delete, owner-scoped). `params` is a JSON facet
dict mirroring the query surface; clean_params() whitelists facet keys so a
saved view can't accumulate junk.

Tests (DB-free): _truthy, clean_params key-whitelisting, saved-filters
auth-guards. UI (facet bar + saved-views sidebar) lands next.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01FRgehjoz7Yv8LkUfADxACm

src/thoughtsync/app.py

@@ -14,6 +14,7 @@ from .db import session_scope
 from .graph import bp as graph_bp
 from .labels import bp as labels_bp
 from .notes import bp as notes_bp
+from .saved_filters import bp as saved_filters_bp
 from .settings import get_public_config, get_setting, load_or_create_secret_key
 from .settings_api import bp as settings_bp
 from .sync import bp as sync_bp
@@ -46,6 +47,7 @@ def create_app() -> Quart:
     app.register_blueprint(graph_bp)
     app.register_blueprint(settings_bp)
     app.register_blueprint(sync_bp)
+    app.register_blueprint(saved_filters_bp)
 
     @app.before_serving
     async def _bootstrap() -> None: