feat: restructure iOS plugin for SPM compatibility - Phase 1

- Create SPM-compliant directory structure: Sources/workmanager_apple/
- Move all Swift files from Classes/ to Sources/workmanager_apple/
- Preserve pigeon subdirectory structure
- Update podspec to reference new file locations: Sources/workmanager_apple/**/*
- Update Pigeon configuration to generate Swift files in new location
- Add comprehensive SPM migration plan documentation

✅ Verified: CocoaPods builds successfully with new structure
✅ Backward compatibility: No breaking changes for existing users

This prepares the foundation for Swift Package Manager support while
maintaining full CocoaPods compatibility.

Author: ened

SPM_MIGRATION_PLAN.md

@@ -0,0 +1,182 @@
+# Swift Package Manager Migration Plan
+
+## Overview
+Migrate `workmanager_apple` plugin to support Swift Package Manager (SPM) while maintaining full CocoaPods backward compatibility.
+
+## Current Structure Analysis
+```
+workmanager_apple/ios/
+├── Assets/
+├── Classes/
+│   ├── BackgroundTaskOperation.swift
+│   ├── BackgroundWorker.swift
+│   ├── Extensions.swift
+│   ├── LoggingDebugHandler.swift
+│   ├── NotificationDebugHandler.swift
+│   ├── SimpleLogger.swift
+│   ├── ThumbnailGenerator.swift
+│   ├── UserDefaultsHelper.swift
+│   ├── WMPError.swift
+│   ├── WorkmanagerDebugHandler.swift
+│   ├── WorkmanagerPlugin.swift
+│   └── pigeon/
+│       └── WorkmanagerApi.g.swift
+├── Resources/
+│   └── PrivacyInfo.xcprivacy
+└── workmanager_apple.podspec
+```
+
+## Migration Strategy
+
+### Phase 1: SPM Structure Setup
+1. Create `workmanager_apple/ios/Package.swift`
+2. Create new directory structure:
+   ```
+   workmanager_apple/ios/
+   ├── Sources/
+   │   └── workmanager_apple/
+   │       ├── include/
+   │       │   └── workmanager_apple-umbrella.h (if needed)
+   │       └── [all .swift files moved here]
+   └── Resources/
+       └── PrivacyInfo.xcprivacy
+   ```
+
+### Phase 2: File Migration
+- **Move Swift files** from `Classes/` to `Sources/workmanager_apple/`
+- **Preserve pigeon structure** as `Sources/workmanager_apple/pigeon/`
+- **Update import statements** if needed
+- **Handle resources** - PrivacyInfo.xcprivacy
+
+### Phase 3: Configuration Files
+- **Create Package.swift** with proper target definitions
+- **Update podspec** to reference new file locations
+- **Maintain backward compatibility** for CocoaPods users
+
+### Phase 4: Testing Strategy
+- **Dual build testing** in GitHub Actions
+- **CocoaPods build**: Test existing workflow
+- **SPM build**: New workflow for SPM validation
+- **Example app testing**: Both dependency managers
+
+## Implementation Details
+
+### Package.swift Configuration
+```swift
+// swift-tools-version: 5.9
+import PackageDescription
+
+let package = Package(
+    name: "workmanager_apple",
+    platforms: [
+        .iOS(.v14)
+    ],
+    products: [
+        .library(name: "workmanager_apple", targets: ["workmanager_apple"])
+    ],
+    targets: [
+        .target(
+            name: "workmanager_apple",
+            resources: [.process("Resources")]
+        )
+    ]
+)
+```
+
+### GitHub Actions Strategy
+
+**Matrix Strategy using Flutter SPM configuration:**
+- **CocoaPods Build**: `flutter config --no-enable-swift-package-manager` + build
+- **SPM Build**: `flutter config --enable-swift-package-manager` + build
+
+**Key Features:**
+1. **Flutter-native approach**: Use `flutter config` flags to switch dependency managers
+2. **Simple validation**: Does example app build and run with both configurations?
+3. **Matrix builds**: Test both `--enable-swift-package-manager` and `--no-enable-swift-package-manager`
+
+**GitHub Actions Matrix:**
+```yaml
+strategy:
+  matrix:
+    spm_enabled: [true, false]
+    include:
+      - spm_enabled: true
+        config_cmd: "flutter config --enable-swift-package-manager"
+        name: "SPM"
+      - spm_enabled: false  
+        config_cmd: "flutter config --no-enable-swift-package-manager"
+        name: "CocoaPods"
+```
+
+## Risk Mitigation
+
+### Backward Compatibility
+- **Keep CocoaPods support** indefinitely
+- **Update podspec paths** to point to new locations
+- **Test both build systems** in CI
+
+### File Organization
+- **Maintain logical grouping** of Swift files
+- **Preserve pigeon integration** with generated files
+- **Handle resources properly** in both systems
+
+### Dependencies
+- **No external Swift dependencies** currently - simplifies migration
+- **Flutter framework dependency** handled by both systems
+
+## Testing Requirements
+
+### Pre-Migration Tests
+- [ ] Current CocoaPods build works
+- [ ] Example app builds and runs
+- [ ] All functionality works on physical device
+
+### Verification Strategy
+**Simple test**: Does the example app build and run with both dependency managers?
+
+**CocoaPods Build:**
+```bash
+flutter config --no-enable-swift-package-manager
+cd example && flutter build ios --debug --no-codesign
+```
+
+**SPM Build:**
+```bash
+flutter config --enable-swift-package-manager
+cd example && flutter build ios --debug --no-codesign
+```
+
+**Flutter Requirements:**
+- Flutter 3.24+ required for SPM support
+- SPM is off by default, must be explicitly enabled
+
+### CI/CD Integration
+- Use Flutter's built-in SPM configuration flags
+- Test both dependency managers via matrix builds
+- No separate long-lived branches needed
+
+## Implementation Phases
+
+### Phase 1: Directory Restructure (First Commit)
+1. Create SPM-compliant directory structure
+2. Move all Swift files to `Sources/workmanager_apple/`
+3. Update podspec to reference new locations
+4. Ensure CocoaPods + Pigeon still work
+5. **Verification**: Example app builds and runs with CocoaPods
+
+### Phase 2: SPM Configuration (Second Commit)
+1. Add `Package.swift` with proper configuration
+2. Handle resources (PrivacyInfo.xcprivacy)
+3. **Verification**: Example app builds and runs with SPM
+
+### Phase 3: CI Integration (Third Commit)
+1. Update GitHub Actions to test both dependency managers
+2. Use Flutter config flags for SPM/CocoaPods selection
+
+## Success Criteria
+- ✅ SPM support working in Flutter projects
+- ✅ Full CocoaPods backward compatibility maintained
+- ✅ All existing functionality preserved
+- ✅ CI/CD tests both dependency managers
+- ✅ No breaking changes for existing users
+- ✅ Proper resource and privacy manifest handling

example/ios/Podfile.lock

@@ -41,7 +41,7 @@ SPEC CHECKSUMS:
   path_provider_foundation: 608fcb11be570ce83519b076ab6a1fffe2474f05
   permission_handler_apple: 4ed2196e43d0651e8ff7ca3483a069d469701f2d
   shared_preferences_foundation: 9e1978ff2562383bd5676f64ec4e9aa8fa06a6f7
-  workmanager_apple: 46692e3180809ea34232c2c29ad16d35ab793ded
+  workmanager_apple: 904529ae31e97fc5be632cf628507652294a0778
 
 PODFILE CHECKSUM: bf5d48b0f58a968d755f5b593e79332a40015529