M9 S3 (backend): organize routes adopt toolkit + shared label reconciliation

DRY across the "organize/recall" backend surface:

- serialize.py (new): serialize_label(label) — the base {id,name,color}
  shape. labels.py builds on it (adds count); sync deltas will (S4).
- labeling.py (new): resolve_owned_label_ids() + reconcile_manual_labels()
  — the "set a note's MANUAL (picker) labels, leave the via_tag rows alone"
  logic was duplicated line-for-line between notes.set_note_labels and
  sync._apply_note_manual_labels. Now one home; both adopt it (removes the
  redundant `chosen`==owned recompute in notes). Behavior-preserving.
- labels.py: json_error/not_found/parse_uuid, colors.normalize_color, and
  serialize_label; dropped local LABEL_COLORS + _normalize_label_color
  (NOTE_COLORS is the single palette) and `import uuid` (rule 22).
- saved_filters.py: json_error/not_found/parse_uuid for its 2 uuid parses
  + error shapes.
- graph.py: no change — no error/uuid/palette-normalize duplication to fold.

Test: DB-free test_serialize_label_shape guards the base shape.
sync.py's reconciliation swap is behavior-identical; operator-verified on
deploy (no Postgres CI lane).

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

src/thoughtsync/sync.py

@@ -21,6 +21,7 @@ from sqlalchemy import func, select
 from .auth import login_required
 from .config import Config
 from .db import session_scope
+from .labeling import reconcile_manual_labels, resolve_owned_label_ids
 from .models.label import Label, NoteLabel
 from .models.note import Note
 from .models.note_attachment import NoteAttachment
@@ -212,20 +213,9 @@ async def _apply_note_manual_labels(db, note: Note, ch: dict) -> None:
         try:
             wanted.add(uuid.UUID(str(r)))
         except (ValueError, TypeError):
-            continue
-    owned: set = set()
-    if wanted:
-        owned = set(
-            (await db.scalars(select(Label.id).where(Label.owner_id == g.user_id, Label.id.in_(wanted)))).all()
-        )
-    existing = (await db.scalars(select(NoteLabel).where(NoteLabel.note_id == note.id))).all()
-    attached = {r.label_id for r in existing}
-    for r in existing:
-        if not r.via_tag and r.label_id not in owned:
-            await db.delete(r)
-    for lid in owned:
-        if lid not in attached:
-            db.add(NoteLabel(note_id=note.id, label_id=lid, via_tag=False))
+            continue  # sync is lenient: skip a malformed id rather than reject the push
+    owned = await resolve_owned_label_ids(db, wanted, g.user_id)
+    await reconcile_manual_labels(db, note, owned)
 
 
 async def _purge_note(db, note: Note, edited_at: datetime | None) -> None: