fix: rename Note.metadata → entity_meta (reserved by SQLAlchemy Declarative API)

SQLAlchemy reserves 'metadata' as a class attribute on declarative models.
Renamed to 'entity_meta' with explicit column name 'metadata' so the DB
column is unchanged but the Python attribute no longer conflicts.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/fabledassistant/models/note.py

@@ -54,7 +54,8 @@ class Note(Base, TimestampMixin):
     # Entity type — 'note' (default), 'person', 'place', 'list'
     note_type: Mapped[str] = mapped_column(Text, default="note", server_default="note")
     # Structured metadata for entity types (person/place/list)
-    metadata: Mapped[dict | None] = mapped_column(JSONB, nullable=True)
+    # Named 'entity_meta' to avoid collision with SQLAlchemy's reserved 'metadata' attribute
+    entity_meta: Mapped[dict | None] = mapped_column("metadata", JSONB, nullable=True)
 
     __table_args__ = (
         Index("ix_notes_tags", "tags", postgresql_using="gin"),
@@ -97,7 +98,7 @@ class Note(Base, TimestampMixin):
             ),
             "is_task": self.is_task,
             "note_type": self.entity_type,
-            "metadata": self.metadata or {},
+            "metadata": self.entity_meta or {},
             "created_at": self.created_at.isoformat(),
             "updated_at": self.updated_at.isoformat(),
         }