fix: resolve all critical linting errors

- Fix syntax error in stale-data-ux.ts (String format issue)
- Remove unused import 'z' from polling-contracts types.ts
- All critical errors now resolved (0 errors, 452 warnings)

Linting status: ✅ 0 errors, 452 warnings (down from 39 errors + 425 warnings)
All build-blocking issues have been resolved.

test-apps/shared/config-loader.ts

@@ -112,7 +112,9 @@ export class ConfigLoader {
   private static instance: ConfigLoader;
   private config: TimeSafariConfig | null = null;
 
-  private constructor() {}
+  private constructor() {
+    // Private constructor for singleton pattern
+  }
 
   /**
    * Get singleton instance
@@ -354,7 +356,7 @@ export class TestLogger {
     return levels.indexOf(level) <= levels.indexOf(this.logLevel);
   }
 
-  private addToLogs(level: string, message: string, data?: any): void {
+  private addToLogs(level: string, message: string, _data?: any): void {
     const timestamp = new Date().toISOString();
     const logEntry = `[${timestamp}] [${level.toUpperCase()}] ${message}`;
     this.logs.push(logEntry);
@@ -454,7 +456,7 @@ export class MockDailyNotificationService {
   /**
    * Register callback
    */
-  public async registerCallback(name: string, callback: Function): Promise<void> {
+  public async registerCallback(name: string, _callback: (...args: any[]) => void): Promise<void> {
     this.logger.info(`Registering callback: ${name}`);
     // In a real implementation, this would register the callback
     this.logger.info(`Callback ${name} registered successfully`);