feat: Azure (Entra ID) login as user login (#16)

Replaces the client-side PIN login with real authentication against Azure
Entra ID via PocketBase's built-in OAuth2 (OIDC) flow. Every Azure user is
auto-provisioned as a team_member on first login.

- pb_migrations: team_members becomes a PocketBase auth collection (OIDC
  provider configured from env); all collections require @request.auth.id
- pb_hooks: provisioning of role (ENTRA_ADMIN_EMAILS allow-list) and
  enrollment_status, with admin-role re-sync on every login
- frontend: "Sign in with Microsoft" login, pb.authStore-based session,
  TeamManager manages roster/roles (no PIN/manual create)
- infra: Entra env wiring + pb_hooks mount for dev (Labs) and prod
- src/lib/azureAuth.js + tests for the canonical role/allow-list logic
- docs/auth-spec.md

Knowledge base, generated tests and micro-learnings are left untouched.
Existing PIN users are dropped (no migration required, per sign-off).

Closes #16

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/pages/Admin/index.jsx

@@ -197,7 +197,7 @@ const Admin = () => {
         {activeTab === 'team' && (
           <div className="animate-in fade-in duration-300 max-w-4xl mx-auto">
             <h1 className="text-3xl text-teal mb-2">Team Management</h1>
-            <p className="text-fg-muted mb-8">Manage team members, roles, and login PINs.</p>
+            <p className="text-fg-muted mb-8">Review team members and manage their roles. Accounts are created automatically via Microsoft (Azure) sign-in.</p>
             <TeamManager />
           </div>
         )}