Add passkey (WebAuthn) authentication with self-registration

Enable users to sign up and sign in using passkeys (biometrics/security
keys) without needing a manually-created Authentik account. The existing
SSO login remains as an alternative.

Backend:
- Add WebAuthn registration/authentication endpoints via py-webauthn
- Issue HS256 JWTs for passkey users, with Redis-backed challenge storage
- Dual JWT verification in auth middleware (issuer-based routing: passkey
  HS256 vs Authentik RS256)
- PasskeyCredential model + migration making user.password nullable
- UserRepository with full CRUD for users and credentials

Frontend:
- AuthUser type abstraction unifying OIDC and passkey users
- Passkey service using @simplewebauthn/browser for WebAuthn ceremonies
- LoginModal redesigned with Sign In / Sign Up tabs
- Type migration from oidc-client-ts User to AuthUser across all services
  and components

crawler/frontend/src/components/TaskIndicator.tsx

@@ -1,8 +1,9 @@
 import { getUser } from '@/auth/authService';
+import { getStoredPasskeyUser } from '@/auth/passkeyService';
+import { fromOidcUser, type AuthUser } from '@/auth/types';
 import { POLLING_INTERVALS } from '@/constants';
 import { fetchTaskStatus, cancelTask, clearAllTasks } from '@/services';
 import { TaskStatus, type TaskResult } from '@/types';
-import type { User } from 'oidc-client-ts';
 import { useEffect, useState } from 'react';
 import { Tooltip, TooltipContent, TooltipProvider, TooltipTrigger } from './ui/tooltip';
 import { Button } from './ui/button';
@@ -15,7 +16,7 @@ interface TaskIndicatorProps {
 }
 
 export function TaskIndicator({ taskID, onTaskCancelled }: TaskIndicatorProps) {
-    const [user, setUser] = useState<User | null>(null);
+    const [user, setUser] = useState<AuthUser | null>(null);
     const [progressPercentage, setProgressPercentage] = useState<number>(0);
     const [processed, setProcessed] = useState<number | null>(null);
     const [total, setTotal] = useState<number | null>(null);
@@ -26,7 +27,14 @@ export function TaskIndicator({ taskID, onTaskCancelled }: TaskIndicatorProps) {
     const [drawerOpen, setDrawerOpen] = useState(false);
 
     useEffect(() => {
-        getUser().then(setUser);
+        const passkeyUser = getStoredPasskeyUser();
+        if (passkeyUser) {
+            setUser(passkeyUser);
+        } else {
+            getUser().then((oidcUser) => {
+                if (oidcUser) setUser(fromOidcUser(oidcUser));
+            });
+        }
     }, []);
 
     useEffect(() => {