Improve subscription UI and fix trial date handling

Lock Screen:
- Add light/dark mode support with adaptive colors
- Make passcode text tappable to trigger authentication

Trial Date Fixes:
- Fix IAPManager to read firstLaunchDate directly from UserDefaults
- Add expiration date check (> Date()) before showing "expires in" text
- Show "Trial expired" when trial end date is in the past
- Disable subscription bypass in DEBUG mode for testing

Month/Year Subscribe Prompts:
- Redesign with gradient icons and compelling copy
- Add fade mask (100% at top to 0% at 50%) for content behind
- Position subscribe overlay on bottom half of screen
- Month: purple/pink theme with calendar icon
- Year: orange/pink theme with chart icon

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

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

Shared/Views/IAPWarningView.swift

@@ -21,15 +21,20 @@ struct IAPWarningView: View {
                 Image(systemName: "clock")
                     .foregroundColor(.orange)
 
-                Text(String(localized: "iap_warning_view_title"))
-                    .font(.body)
-                    .foregroundColor(textColor)
+                if let expirationDate = iapManager.trialExpirationDate, expirationDate > Date() {
+                    Text(String(localized: "iap_warning_view_title"))
+                        .font(.body)
+                        .foregroundColor(textColor)
 
-                if let expirationDate = iapManager.trialExpirationDate {
                     Text(expirationDate, style: .relative)
                         .font(.body)
                         .bold()
                         .foregroundColor(.orange)
+                } else {
+                    Text(String(localized: "purchase_view_trial_expired"))
+                        .font(.body)
+                        .bold()
+                        .foregroundColor(.orange)
                 }
             }