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/models/project.py

@@ -1,6 +1,5 @@
 import enum
-from datetime import datetime
-from sqlalchemy import DateTime, ForeignKey, Integer, Text
+from sqlalchemy import ForeignKey, Integer, Text
 from sqlalchemy.orm import Mapped, mapped_column
 from scribe.models import Base
 from scribe.models.base import TimestampMixin, SoftDeleteMixin
@@ -22,10 +21,6 @@ class Project(Base, TimestampMixin, SoftDeleteMixin):
     goal: Mapped[str] = mapped_column(Text, default="")
     status: Mapped[str] = mapped_column(Text, default="active")
     color: Mapped[str | None] = mapped_column(Text, nullable=True)  # hex color
-    auto_summary: Mapped[str | None] = mapped_column(Text, nullable=True, default=None)
-    summary_updated_at: Mapped[datetime | None] = mapped_column(
-        DateTime(timezone=True), nullable=True, default=None
-    )
 
     def to_dict(self) -> dict:
         return {
@@ -36,7 +31,6 @@ class Project(Base, TimestampMixin, SoftDeleteMixin):
             "goal": self.goal,
             "status": self.status,
             "color": self.color,
-            "auto_summary": self.auto_summary,
             "created_at": self.created_at.isoformat(),
             "updated_at": self.updated_at.isoformat(),
         }