Add PostgreSQL memory system for persistent user and conversation storage

- Add PostgreSQL database with SQLAlchemy async support
- Create models: User, UserFact, UserPreference, Conversation, Message, Guild, GuildMember
- Add custom name support so bot knows 'who is who'
- Add user facts system for remembering things about users
- Add persistent conversation history that survives restarts
- Add memory commands cog (!setname, !remember, !whatdoyouknow, !forgetme)
- Add admin commands (!setusername, !teachbot)
- Set up Alembic for database migrations
- Update docker-compose with PostgreSQL service
- Gracefully falls back to in-memory storage when DB not configured

src/daemon_boyfriend/models/__init__.py

@@ -0,0 +1,17 @@
+"""Database models."""
+
+from .base import Base
+from .conversation import Conversation, Message
+from .guild import Guild, GuildMember
+from .user import User, UserFact, UserPreference
+
+__all__ = [
+    "Base",
+    "Conversation",
+    "Guild",
+    "GuildMember",
+    "Message",
+    "User",
+    "UserFact",
+    "UserPreference",
+]