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>

frontend/src/components/AdminRoute.tsx

@@ -0,0 +1,13 @@
+import type { ReactNode } from 'react'
+import { Navigate } from 'react-router-dom'
+import { useAuth } from '../context/AuthContext'
+
+export function AdminRoute({ children }: { children: ReactNode }) {
+  const { user, loading } = useAuth()
+
+  if (loading) return <p>Loading...</p>
+  if (!user) return <Navigate to="/login" replace />
+  if (!user.is_site_admin) return <Navigate to="/rooms" replace />
+
+  return <>{children}</>
+}

frontend/src/components/TopBar.tsx

@@ -1,4 +1,5 @@
 import { useEffect, useState } from 'react'
+import { useNavigate } from 'react-router-dom'
 import logo from '../assets/logo.png'
 import { useAuth } from '../context/AuthContext'
 import { initials } from '../lib/avatar'
@@ -7,6 +8,7 @@ import './TopBar.css'
 
 export function TopBar() {
   const { user, logout } = useAuth()
+  const navigate = useNavigate()
   const [menuOpen, setMenuOpen] = useState(false)
   const [pushSubscribed, setPushSubscribed] = useState(false)
   const [pushBusy, setPushBusy] = useState(false)
@@ -58,6 +60,18 @@ export function TopBar() {
             <div className="top-bar-menu-scrim" onClick={() => setMenuOpen(false)} />
             <div className="top-bar-menu" role="menu">
               <div className="top-bar-menu-username">{user.username}</div>
+              {user.is_site_admin && (
+                <button
+                  type="button"
+                  role="menuitem"
+                  onClick={() => {
+                    setMenuOpen(false)
+                    navigate('/admin')
+                  }}
+                >
+                  Admin
+                </button>
+              )}
               {isPushSupported() && (
                 <button
                   type="button"