docs(ios): add comprehensive iOS code signing guide

Created iOS code signing documentation:

Signing Scenarios:
- Simulator builds (signing disabled - faster)
- Device builds with automatic signing (recommended)
- Device builds with manual signing (advanced)

Configuration:
- Command-line build flags for each scenario
- Xcode project settings
- Environment variables

Troubleshooting:
- Common signing errors and solutions
- Certificate and provisioning profile issues
- Bundle identifier conflicts
- Verification commands

Quick Reference:
- Simulator: CODE_SIGNING_REQUIRED=NO
- Device (auto): CODE_SIGN_STYLE=Automatic + DEVELOPMENT_TEAM
- Device (manual): CODE_SIGN_STYLE=Manual + PROVISIONING_PROFILE

Updated SETUP.md:
- Added code signing section
- Quick reference for simulator vs device builds
- Link to comprehensive guide

Result: Complete signing guide for all iOS build scenarios

test-apps/ios-test-app/SETUP.md

@@ -252,6 +252,51 @@ iOS handles background execution differently than Android:
 - **UserDefaults**: For schedules and configuration (like Android's SharedPreferences)
 - **Core Data**: For content cache and history (like Android's Room database)
 
+## Code Signing
+
+### Simulator Builds (Default)
+
+**No signing required** - The build scripts automatically disable signing for simulator builds:
+
+```bash
+CODE_SIGN_IDENTITY=""
+CODE_SIGNING_REQUIRED=NO
+CODE_SIGNING_ALLOWED=NO
+```
+
+This is handled automatically by the build scripts.
+
+### Device Builds
+
+**For physical devices, you need proper signing:**
+
+1. **Open project in Xcode:**
+   ```bash
+   cd test-apps/ios-test-app/App
+   open App.xcworkspace
+   ```
+
+2. **Configure signing:**
+   - Select project in navigator
+   - Select target "App"
+   - Go to "Signing & Capabilities" tab
+   - Check "Automatically manage signing"
+   - Select your Team (Apple Developer account)
+
+3. **Build for device:**
+   ```bash
+   xcodebuild -workspace App.xcworkspace \
+       -scheme App \
+       -sdk iphoneos \
+       -configuration Debug \
+       -destination 'generic/platform=iOS' \
+       CODE_SIGN_STYLE=Automatic \
+       DEVELOPMENT_TEAM="YOUR_TEAM_ID" \
+       clean build
+   ```
+
+**See `docs/IOS_CODE_SIGNING.md` for complete signing guide.**
+
 ## Troubleshooting
 
 ### Plugin Not Found