feat: implement privacy-aware profile visibility and activity status filtering using optional authentication guard

src/auth/guards/optional-auth.guard.ts

@@ -0,0 +1,18 @@
+import { Injectable, ExecutionContext } from '@nestjs/common';
+import { AuthGuard } from '@nestjs/passport';
+
+/**
+ * Optional JWT auth guard — extracts user if token is present, but doesn't reject if missing.
+ * Use on public endpoints that behave differently for authenticated users (e.g., privacy filtering).
+ */
+@Injectable()
+export class OptionalAuthGuard extends AuthGuard('jwt') {
+  canActivate(context: ExecutionContext) {
+    return super.canActivate(context);
+  }
+
+  handleRequest(err: any, user: any) {
+    // Don't throw on missing/invalid token — just return null
+    return user || null;
+  }
+}