feat: improve documentation UX and content quality

- Add dark blue theme with higher contrast (#1e3a8a primary)
- Remove redundant cross-links between use case pages (handled by sidebar)
- Eliminate repetitive intro paragraph from quickstart page
- Add Xcode Help link for Background Modes configuration
- Add explanatory callout for iOS task identifier requirements
- Improve user guidance and reduce confusion

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: ened

docs.json

@@ -1,6 +1,10 @@
 {
   "name": "Flutter Workmanager",
   "description": "Background task execution for Flutter apps",
+  "theme": {
+    "primaryColor": "#1e3a8a",
+    "accentColor": "#3b82f6"
+  },
   "sidebar": [
     {
       "group": "Getting Started",

docs/quickstart.mdx

@@ -3,8 +3,6 @@ title: Quick Start
 description: Get started with Flutter Workmanager in minutes
 ---
 
-Get Flutter Workmanager up and running in your app quickly.
-
 ## Installation
 
 Add `workmanager` to your `pubspec.yaml`:
@@ -29,7 +27,7 @@ Android works automatically - no additional setup required! ✅
 ### iOS
 iOS requires a 5-minute setup in Xcode:
 
-1. **Enable Background Modes** in Xcode target capabilities:
+1. **Enable Background Modes** in Xcode target capabilities ([Xcode Help](https://help.apple.com/xcode/mac/current/#/devbfa1532c4)):
    - Background processing ✅
    - Background fetch ✅
 
@@ -57,6 +55,8 @@ WorkmanagerPlugin.registerBGProcessingTask(
 )
 ```
 
+> **Why this configuration is needed:** iOS requires explicit registration of background task identifiers for security and system resource management. The task identifier in Info.plist tells iOS which background tasks your app can schedule, while the AppDelegate registration connects the identifier to the actual task handler. This prevents apps from scheduling unauthorized background work.
+
 ## Basic Usage
 
 ### 1. Create Background Task Handler

docs/usecases/data-sync.mdx

@@ -334,7 +334,3 @@ Future<bool> _performIncrementalSync() async {
 - Use compression for large payloads
 - Cache API responses appropriately
 
-## Related Use Cases
-
-- **[Upload Files](upload-files)** - Upload user content in the background
-- **[Fetch Notifications](fetch-notifications)** - Check for new notifications from your server

docs/usecases/upload-files.mdx

@@ -265,7 +265,3 @@ Future<bool> _uploadWithRetry(Map<String, dynamic> inputData) async {
 }
 ```
 
-## Related Use Cases
-
-- **[Data Sync](data-sync)** - Synchronize data with your backend
-- **[Database Maintenance](database-maintenance)** - Clean up and optimize local data