feat(auth): add password strength indicator and magic links

Password strength (zxcvbn-ts):
- PasswordStrength component with 4-segment color bar and German feedback
- Lazy-loaded with 150ms debounce to avoid SSR/bundle issues
- Integrated into RegisterPage and ChangePassword components

Magic Links (passwordless email):
- Better Auth magicLink plugin (10-minute expiry)
- sendMagicLinkEmail() in email service (German template)
- Passthrough route for /magic-link/* endpoints
- sendMagicLink() in shared-auth client
- "Login-Link per E-Mail senden" button on all 20 login pages
- All 21 auth stores have sendMagicLink() method

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/presi/apps/web/src/lib/stores/auth.svelte.ts

@@ -142,6 +142,12 @@ export const auth = {
 		return result;
 	},
 
+	async sendMagicLink(email: string) {
+		const authService = getAuthService();
+		if (!authService) return { success: false, error: 'Auth not available on server' };
+		return authService.sendMagicLink(email);
+	},
+
 	isPasskeyAvailable(): boolean {
 		const authService = getAuthService();
 		if (!authService) return false;

apps/presi/apps/web/src/routes/(auth)/login/+page.svelte

@@ -44,6 +44,7 @@
 	onSignInWithPasskey={() => auth.signInWithPasskey()}
 	onVerifyTwoFactor={(code, trust) => auth.verifyTwoFactor(code, trust)}
 	onVerifyBackupCode={(code) => auth.verifyBackupCode(code)}
+	onSendMagicLink={(email) => auth.sendMagicLink(email)}
 	{goto}
 	successRedirect={redirectTo}
 	registerPath="/register"