feat(monetization-261): prepare entitlement infrastructure and quota enforcement for release

- Add EntitlementSnapshot, EntitlementRevalidationUseCase, and BillingUseCases
- Add DriftEntitlementSnapshotRepository for offline entitlement caching
- Add HealthConnect gateway and integration
- Add quota enforcement in share acceptance (server and UI)
- Add entitlement API endpoints in server
- Add privacy policy v1 and release compliance checklist
- Add QA gates and device runbooks for release validation
- Add demo content screen and settings screen

Ticket #261

lib/infrastructure/remote/http_api_client.dart

@@ -2,6 +2,7 @@ import 'dart:async';
 import 'dart:convert';
 import 'dart:io';
 
+import 'package:flutter/foundation.dart';
 import 'package:http/http.dart' as http;
 
 import '../../application/application.dart';
@@ -27,11 +28,20 @@ final class HttpApiClient {
   static String defaultBaseUrlFor({
     required bool isAndroid,
     String configuredBaseUrl = _configuredBaseUrl,
+    bool isReleaseMode = kReleaseMode,
   }) {
     final configured = configuredBaseUrl.trim();
     if (configured.isNotEmpty) {
+      if (isReleaseMode && Uri.tryParse(configured)?.scheme != 'https') {
+        throw StateError(
+          'GAMETIME_API_BASE_URL must be an HTTPS URL in release builds.',
+        );
+      }
       return configured;
     }
+    if (isReleaseMode) {
+      throw StateError('GAMETIME_API_BASE_URL is required in release builds.');
+    }
     if (isAndroid) {
       return androidEmulatorDefaultBaseUrl;
     }