feat(test): add localhost testing support for prefetch

- Add serverMode configuration to test-user-zero config
  - Supports: localhost, staging, production, mock, custom
  - Auto-detects platform (Android/iOS/Web) for localhost URLs
  - Android emulator uses 10.0.2.2 for host machine localhost

- Add getApiServerUrl() helper function
  - Returns correct URL based on serverMode and platform
  - Handles Android emulator special case (10.0.2.2)

- Update TestUserZeroAPI to respect serverMode
  - Checks mock mode before making network calls
  - Uses getApiServerUrl() for base URL resolution
  - Allows runtime URL switching via setBaseUrl()

- Add localhost testing configuration
  - Configurable port and HTTPS settings
  - Development mode headers support

- Create localhost testing guide
  - Step-by-step setup instructions
  - Platform-specific localhost addresses explained
  - Quick test API server example
  - Troubleshooting common issues
  - Monitoring prefetch execution commands

- Update Capacitor config to use getApiServerUrl()
  - Fixes breaking change from api.server removal

This enables testing prefetch functionality with a local development
API server running on localhost, perfect for development and debugging
of the 5-minute prefetch scheduling feature.

test-apps/daily-notification-test/capacitor.config.ts

@@ -18,7 +18,8 @@ const config: CapacitorConfig = {
       timesafariConfig: {
         activeDid: TEST_USER_ZERO_CONFIG.identity.did,
         endpoints: {
-          projectsLastUpdated: `${TEST_USER_ZERO_CONFIG.api.server}${TEST_USER_ZERO_CONFIG.api.starsEndpoint}`
+          // Use getApiServerUrl() to get correct URL based on serverMode
+          projectsLastUpdated: `${TEST_USER_ZERO_CONFIG.getApiServerUrl()}${TEST_USER_ZERO_CONFIG.api.starsEndpoint}`
         },
         starredProjectsConfig: {
           enabled: true,