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>

tests/test_embeddings.py

@@ -62,22 +62,6 @@ async def test_get_embedding_returns_list_of_floats():
     fake_embedder.embed.assert_called_once_with(["hello world"])
 
 
-@pytest.mark.asyncio
-async def test_get_embedding_ignores_legacy_model_param():
-    """The `model` kwarg is preserved for backward-compat but should not affect
-    the fastembed call."""
-    fake_vec = MagicMock()
-    fake_vec.tolist.return_value = [0.0]
-    fake_embedder = MagicMock()
-    fake_embedder.embed = MagicMock(return_value=iter([fake_vec]))
-    with patch(
-        "scribe.services.embeddings._get_model",
-        AsyncMock(return_value=fake_embedder),
-    ):
-        out = await get_embedding("x", model="ignored-model-name")
-    assert out == [0.0]
-
-
 @pytest.mark.asyncio
 async def test_get_embedding_propagates_model_load_failures():
     """If fastembed can't initialize, the error propagates — callers catch