Phase 1 MVP - Complete implementation

- Auth: register, login, JWT with refresh tokens, blocklist
- Projects/Folders/Documents CRUD with soft deletes
- Tags CRUD and assignment
- FTS5 search with highlights and tag filtering
- ADR-001, ADR-002, ADR-003 compliant
- Security fixes applied (JWT_SECRET_KEY, exception handler, cookie secure)
- 25 tests passing

app/models/agent.py

@@ -0,0 +1,25 @@
+import uuid
+from datetime import datetime
+
+from sqlalchemy import Boolean, DateTime, String, Text
+from sqlalchemy.orm import Mapped, mapped_column
+
+from app.database import Base
+
+
+def generate_uuid() -> str:
+    return str(uuid.uuid4())
+
+
+class Agent(Base):
+    __tablename__ = "agents"
+
+    id: Mapped[str] = mapped_column(String(36), primary_key=True, default=generate_uuid)
+    username: Mapped[str] = mapped_column(String(255), unique=True, nullable=False)
+    password_hash: Mapped[str] = mapped_column(Text, nullable=False)
+    role: Mapped[str] = mapped_column(String(20), nullable=False, default="agent")
+    is_deleted: Mapped[bool] = mapped_column(Boolean, default=False, nullable=False)
+    deleted_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+    deleted_by: Mapped[str | None] = mapped_column(String(36), nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, nullable=False)
+    updated_at: Mapped[datetime] = mapped_column(DateTime, default=datetime.utcnow, onupdate=datetime.utcnow, nullable=False)