chore: remove pre-pivot dead code + finish Scribe rebrand (#599 t1-3)

- Header wordmark Fabled -> Scribe; fable:calendar-changed event ->
  scribe:calendar-changed; SettingsView CSS comment.
- Drop dead Project.auto_summary + summary_updated_at columns (migration
  0063) -- the Ollama-era summarizer is gone; model + 2 frontend types +
  projects test updated.
- Remove pivot vestiges: diagnostics _curator_busy()/curator_busy
  heartbeat field, tz BRIEFING_DAY_START_HOUR/user_briefing_date dead
  aliases, the ignored 'model' param on get_embedding (+ its test).

ruff src/ clean; CI is the gate. Part of scribe plan #599.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/scribe/services/embeddings.py

@@ -53,12 +53,9 @@ async def _get_model():
     return _model
 
 
-async def get_embedding(text: str, model: str | None = None) -> list[float]:
+async def get_embedding(text: str) -> list[float]:
     """Get an embedding vector for the given text.
 
-    The ``model`` parameter is preserved for backward compatibility with the
-    Ollama era but is now ignored — fastembed uses a single fixed model.
-
     Raises if the fastembed model fails to load. Callers should catch and
     degrade to keyword search.
     """