Fix build errors, resolve all warnings, and improve code quality

Widget Extension Fixes:
- Create standalone WidgetDataProvider for widget data isolation
- Add WIDGET_EXTENSION compiler flag for conditional compilation
- Fix DataController references in widget-shared files
- Sync widget version numbers with main app (23, 1.0.2)
- Add WidgetBackground color to asset catalog

Warning Resolutions:
- Fix UIScreen.main deprecation in BGView and SharingListView
- Fix Text '+' concatenation deprecation in PurchaseButtonView and SettingsTabView
- Fix exhaustive switch in BiometricAuthManager (add .none case)
- Fix var to let in ExportService (3 instances)
- Fix unused result warning in NoteEditorView
- Fix ForEach duplicate ID warnings in MonthView and YearView

Code Quality Improvements:
- Wrap bypassSubscription in #if DEBUG for security
- Rename StupidAssCustomWidgetObservableObject to CustomWidgetStateViewModel
- Add @MainActor to IconViewModel
- Replace fatalError with graceful fallback in SharedModelContainer
- Add [weak self] to closures in DayViewViewModel
- Add OSLog-based AppLogger for production logging
- Add ImageCache with NSCache for memory efficiency
- Add AccessibilityHelpers with Reduce Motion support
- Create DataControllerProtocol for dependency injection
- Update .gitignore with secrets exclusions

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

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Shared/Services/ExportService.swift

@@ -277,7 +277,7 @@ class ExportService {
     // MARK: - PDF Drawing: Mood Distribution Chart
 
     private func drawMoodDistributionChart(at y: CGFloat, stats: ExportStats, margin: CGFloat, width: CGFloat, in context: UIGraphicsPDFRendererContext) -> CGFloat {
-        var currentY = drawSectionTitle("Mood Distribution", at: y, margin: margin)
+        let currentY = drawSectionTitle("Mood Distribution", at: y, margin: margin)
 
         let chartHeight: CGFloat = 140
         let barHeight: CGFloat = 22
@@ -334,7 +334,7 @@ class ExportService {
     // MARK: - PDF Drawing: Weekday Analysis
 
     private func drawWeekdayAnalysis(at y: CGFloat, entries: [MoodEntryModel], margin: CGFloat, width: CGFloat, in context: UIGraphicsPDFRendererContext) -> CGFloat {
-        var currentY = drawSectionTitle("Mood by Day of Week", at: y, margin: margin)
+        let currentY = drawSectionTitle("Mood by Day of Week", at: y, margin: margin)
 
         let weekdays = ["Sun", "Mon", "Tue", "Wed", "Thu", "Fri", "Sat"]
         var weekdayAverages: [Double] = Array(repeating: 0, count: 7)
@@ -488,7 +488,7 @@ class ExportService {
     // MARK: - PDF Drawing: Streaks Section
 
     private func drawStreaksSection(at y: CGFloat, stats: ExportStats, margin: CGFloat, width: CGFloat, in context: UIGraphicsPDFRendererContext) -> CGFloat {
-        var currentY = drawSectionTitle("Streaks & Consistency", at: y, margin: margin)
+        let currentY = drawSectionTitle("Streaks & Consistency", at: y, margin: margin)
 
         let cardWidth = (width - 15) / 2
         let cardHeight: CGFloat = 60