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>

packages/shared-auth-ui/package.json

@@ -32,6 +32,9 @@
 		"typescript": "^5.7.3"
 	},
 	"dependencies": {
+		"@zxcvbn-ts/core": "^3.0.4",
+		"@zxcvbn-ts/language-common": "^3.0.4",
+		"@zxcvbn-ts/language-de": "^3.0.2",
 		"qrcode": "^1.5.4"
 	}
 }