feat: add conversation_type and briefing_date to Conversation model

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

src/fabledassistant/models/conversation.py

@@ -1,4 +1,6 @@
-from sqlalchemy import ForeignKey, Index, Integer, Text
+import datetime
+
+from sqlalchemy import Date, ForeignKey, Index, Integer, Text
 from sqlalchemy import inspect
 from sqlalchemy.dialects.postgresql import JSONB
 from sqlalchemy.orm import Mapped, mapped_column, relationship
@@ -16,6 +18,11 @@ class Conversation(Base, TimestampMixin):
     )
     title: Mapped[str] = mapped_column(Text, default="")
     model: Mapped[str] = mapped_column(Text, default="")
+    # 'chat' (default) or 'briefing'. Briefing conversations are hidden from
+    # the main chat view and managed by the briefing pipeline.
+    conversation_type: Mapped[str] = mapped_column(Text, default="chat", server_default="chat")
+    # For briefing conversations only: the calendar date this briefing covers.
+    briefing_date: Mapped[datetime.date | None] = mapped_column(Date, nullable=True)
 
     messages: Mapped[list["Message"]] = relationship(
         back_populates="conversation",
@@ -38,6 +45,8 @@ class Conversation(Base, TimestampMixin):
             "id": self.id,
             "title": self.title,
             "model": self.model,
+            "conversation_type": self.conversation_type,
+            "briefing_date": self.briefing_date.isoformat() if self.briefing_date else None,
             "message_count": msg_count,
             "created_at": self.created_at.isoformat(),
             "updated_at": self.updated_at.isoformat(),