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/user.py

@@ -0,0 +1,83 @@
+"""User-related database models."""
+
+from datetime import datetime
+from typing import TYPE_CHECKING
+
+from sqlalchemy import BigInteger, Boolean, Float, ForeignKey, String, Text, UniqueConstraint
+from sqlalchemy.orm import Mapped, mapped_column, relationship
+
+from .base import Base
+
+if TYPE_CHECKING:
+    from .conversation import Conversation, Message
+    from .guild import GuildMember
+
+
+class User(Base):
+    """Discord user tracking."""
+
+    __tablename__ = "users"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    discord_id: Mapped[int] = mapped_column(BigInteger, unique=True, index=True)
+    discord_username: Mapped[str] = mapped_column(String(255))
+    discord_display_name: Mapped[str | None] = mapped_column(String(255))
+    custom_name: Mapped[str | None] = mapped_column(String(255))
+    first_seen_at: Mapped[datetime] = mapped_column(default=datetime.utcnow)
+    last_seen_at: Mapped[datetime] = mapped_column(default=datetime.utcnow)
+    is_active: Mapped[bool] = mapped_column(Boolean, default=True)
+
+    # Relationships
+    preferences: Mapped[list["UserPreference"]] = relationship(
+        back_populates="user", cascade="all, delete-orphan"
+    )
+    facts: Mapped[list["UserFact"]] = relationship(
+        back_populates="user", cascade="all, delete-orphan"
+    )
+    conversations: Mapped[list["Conversation"]] = relationship(
+        back_populates="user", cascade="all, delete-orphan"
+    )
+    messages: Mapped[list["Message"]] = relationship(back_populates="user")
+    guild_memberships: Mapped[list["GuildMember"]] = relationship(
+        back_populates="user", cascade="all, delete-orphan"
+    )
+
+    @property
+    def display_name(self) -> str:
+        """Get the name to use when addressing this user."""
+        return self.custom_name or self.discord_display_name or self.discord_username
+
+
+class UserPreference(Base):
+    """Per-user preferences/settings."""
+
+    __tablename__ = "user_preferences"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"), index=True)
+    preference_key: Mapped[str] = mapped_column(String(100))
+    preference_value: Mapped[str | None] = mapped_column(Text)
+
+    # Relationships
+    user: Mapped["User"] = relationship(back_populates="preferences")
+
+    __table_args__ = (UniqueConstraint("user_id", "preference_key"),)
+
+
+class UserFact(Base):
+    """Facts the bot has learned about users."""
+
+    __tablename__ = "user_facts"
+
+    id: Mapped[int] = mapped_column(primary_key=True)
+    user_id: Mapped[int] = mapped_column(ForeignKey("users.id", ondelete="CASCADE"), index=True)
+    fact_type: Mapped[str] = mapped_column(String(50), index=True)  # general, preference, hobby
+    fact_content: Mapped[str] = mapped_column(Text)
+    confidence: Mapped[float] = mapped_column(Float, default=1.0)
+    source: Mapped[str] = mapped_column(String(50), default="conversation")
+    is_active: Mapped[bool] = mapped_column(Boolean, default=True, index=True)
+    learned_at: Mapped[datetime] = mapped_column(default=datetime.utcnow)
+    last_referenced_at: Mapped[datetime | None] = mapped_column(default=None)
+
+    # Relationships
+    user: Mapped["User"] = relationship(back_populates="facts")