Phase 6: Admin portal

Adds is_site_admin-gated site administration: user management (list,
deactivate/reactivate, reset password, promote/demote), room management
(list all rooms including private ones, archive/unarchive, force-transfer
ownership), and an audit log of every admin action.

Backend: User.is_active (deactivation) and Room.is_archived (archive) are
new columns; AdminAuditLog is a new table matching ARCHITECTURE.md's
admin_audit_log design, written to in the same transaction as every
mutating admin action. require_site_admin (dependencies.py) gates all
/api/admin/* routes. get_current_user now rechecks is_active on every
request, so deactivating a user kills their already-open session
immediately, not just future logins. An admin can't deactivate or demote
their own account (the one self-lockout guard included). Archived rooms
drop out of the open-room browse list but stay readable for existing
members.

Frontend: new /admin route (AdminRoute guard, redirects non-admins to
/rooms) with a tabbed Users / Rooms / Audit log / Settings page, plus an
"Admin" link in the account menu for site admins.

Bot/integration management and system settings -- both listed in the
original issue -- are intentionally not here: bot management has nothing
to manage until Phase 7 builds the actual bot data model, and there's no
settings storage or concrete setting to configure yet. Settings has an
empty placeholder tab; bot management is deferred entirely to Phase 7.
Confirmed this scope cut with the repo owner before implementing.

New tests/test_admin.py (14 tests, full suite now 58/58) covers every
admin endpoint's permission gate, the self-action guards, deactivation's
immediate effect on an already-open session, and that every mutating
action produces exactly one audit log row.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

backend/app/services/admin_service.py

@@ -0,0 +1,171 @@
+import uuid
+
+from sqlalchemy import func, select
+from sqlalchemy.ext.asyncio import AsyncSession
+from sqlalchemy.orm import selectinload
+
+from app.models import AdminAuditLog, Room, RoomMembership, RoomRole, User
+from app.security import hash_password
+
+
+class UserNotFoundError(Exception):
+    pass
+
+
+class RoomNotFoundError(Exception):
+    pass
+
+
+class CannotActOnSelfError(Exception):
+    pass
+
+
+class TargetNotRoomMemberError(Exception):
+    pass
+
+
+async def _get_user(db: AsyncSession, user_id: uuid.UUID) -> User:
+    user = await db.get(User, user_id)
+    if user is None:
+        raise UserNotFoundError()
+    return user
+
+
+async def _get_room(db: AsyncSession, room_id: uuid.UUID) -> Room:
+    room = await db.get(Room, room_id)
+    if room is None:
+        raise RoomNotFoundError()
+    return room
+
+
+async def _get_membership(
+    db: AsyncSession, room_id: uuid.UUID, user_id: uuid.UUID
+) -> RoomMembership:
+    result = await db.execute(
+        select(RoomMembership).where(
+            RoomMembership.room_id == room_id, RoomMembership.user_id == user_id
+        )
+    )
+    membership = result.scalar_one_or_none()
+    if membership is None:
+        raise TargetNotRoomMemberError()
+    return membership
+
+
+def _log(
+    db: AsyncSession,
+    actor: User,
+    action: str,
+    target_type: str,
+    target_id: uuid.UUID,
+    metadata: dict | None = None,
+) -> None:
+    db.add(
+        AdminAuditLog(
+            actor_id=actor.id,
+            action=action,
+            target_type=target_type,
+            target_id=target_id,
+            metadata_=metadata,
+        )
+    )
+
+
+async def list_users(db: AsyncSession) -> list[User]:
+    result = await db.execute(select(User).order_by(User.created_at))
+    return list(result.scalars().all())
+
+
+async def set_user_active(
+    db: AsyncSession, actor: User, target_user_id: uuid.UUID, active: bool
+) -> User:
+    if target_user_id == actor.id:
+        raise CannotActOnSelfError()
+    user = await _get_user(db, target_user_id)
+    user.is_active = active
+    _log(db, actor, "user.activate" if active else "user.deactivate", "user", user.id)
+    await db.commit()
+    await db.refresh(user)
+    return user
+
+
+async def reset_user_password(
+    db: AsyncSession, actor: User, target_user_id: uuid.UUID, new_password: str
+) -> None:
+    user = await _get_user(db, target_user_id)
+    user.password_hash = hash_password(new_password)
+    _log(db, actor, "user.reset_password", "user", user.id)
+    await db.commit()
+
+
+async def set_user_site_admin(
+    db: AsyncSession, actor: User, target_user_id: uuid.UUID, is_admin: bool
+) -> User:
+    if target_user_id == actor.id:
+        raise CannotActOnSelfError()
+    user = await _get_user(db, target_user_id)
+    user.is_site_admin = is_admin
+    _log(db, actor, "user.promote" if is_admin else "user.demote", "user", user.id)
+    await db.commit()
+    await db.refresh(user)
+    return user
+
+
+async def list_rooms_admin(db: AsyncSession) -> list[tuple[Room, int]]:
+    result = await db.execute(
+        select(Room, func.count(RoomMembership.user_id))
+        .outerjoin(RoomMembership, RoomMembership.room_id == Room.id)
+        .group_by(Room.id)
+        .order_by(Room.created_at)
+    )
+    return [(room, count) for room, count in result.all()]
+
+
+async def set_room_archived(
+    db: AsyncSession, actor: User, room_id: uuid.UUID, archived: bool
+) -> Room:
+    room = await _get_room(db, room_id)
+    room.is_archived = archived
+    _log(db, actor, "room.archive" if archived else "room.unarchive", "room", room.id)
+    await db.commit()
+    await db.refresh(room)
+    return room
+
+
+async def transfer_ownership_admin(
+    db: AsyncSession, actor: User, room_id: uuid.UUID, new_owner_id: uuid.UUID
+) -> Room:
+    room = await _get_room(db, room_id)
+    # Same invariant as the member-initiated room_service.transfer_ownership
+    # (new owner must already be a member) -- this is the admin override for
+    # the "acting user must currently be the owner" gate, not for that one.
+    new_owner_membership = await _get_membership(db, room_id, new_owner_id)
+    current_owner_membership = await _get_membership(db, room_id, room.owner_id)
+
+    new_owner_membership.role = RoomRole.owner
+    current_owner_membership.role = RoomRole.admin
+    room.owner_id = new_owner_id
+    _log(
+        db,
+        actor,
+        "room.transfer_ownership",
+        "room",
+        room.id,
+        {"new_owner_id": str(new_owner_id)},
+    )
+    await db.commit()
+    await db.refresh(room)
+    return room
+
+
+async def list_audit_log(
+    db: AsyncSession, limit: int = 50, offset: int = 0
+) -> list[AdminAuditLog]:
+    result = await db.execute(
+        select(AdminAuditLog)
+        .options(selectinload(AdminAuditLog.actor))
+        .order_by(AdminAuditLog.created_at.desc())
+        .limit(limit)
+        .offset(offset)
+    )
+    return list(result.scalars().all())

backend/app/services/auth_service.py

@@ -15,6 +15,10 @@ class InvalidCredentialsError(Exception):
     pass
 
 
+class AccountDeactivatedError(Exception):
+    pass
+
+
 async def register_user(db: AsyncSession, data: UserCreate) -> User:
     user = User(
         username=data.username,
@@ -43,4 +47,6 @@ async def authenticate_user(
     user = result.scalar_one_or_none()
     if user is None or not verify_password(password, user.password_hash):
         raise InvalidCredentialsError()
+    if not user.is_active:
+        raise AccountDeactivatedError()
     return user

backend/app/services/room_service.py

@@ -60,7 +60,7 @@ async def create_room(db: AsyncSession, owner_id: uuid.UUID, data: RoomCreate) -
 async def list_open_rooms(db: AsyncSession, user_id: uuid.UUID) -> list[tuple[Room, bool]]:
     result = await db.execute(
         select(Room)
-        .where(Room.is_private.is_(False))
+        .where(Room.is_private.is_(False), Room.is_archived.is_(False))
         .options(selectinload(Room.memberships))
         .order_by(Room.created_at)
     )