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/MonthView/MonthView.swift

@@ -109,6 +109,21 @@ struct MonthView: View {
                     )
                 }
                 .scrollDisabled(iapManager.shouldShowPaywall)
+                .mask(
+                    // Fade effect when paywall should show: 100% at top, 0% halfway down
+                    iapManager.shouldShowPaywall ?
+                    AnyView(
+                        LinearGradient(
+                            gradient: Gradient(stops: [
+                                .init(color: .black, location: 0),
+                                .init(color: .black, location: 0.3),
+                                .init(color: .clear, location: 0.5)
+                            ]),
+                            startPoint: .top,
+                            endPoint: .bottom
+                        )
+                    ) : AnyView(Color.black)
+                )
             }
 
             // Hidden text to trigger updates when custom tint changes
@@ -116,27 +131,72 @@ struct MonthView: View {
                 .hidden()
 
             if iapManager.shouldShowPaywall {
-                // Paywall overlay - tap to show subscription store
-                Color.black.opacity(0.3)
-                    .ignoresSafeArea()
-                    .onTapGesture {
-                        showSubscriptionStore = true
+                // Premium month history prompt - bottom half
+                VStack(spacing: 20) {
+                    // Icon
+                    ZStack {
+                        Circle()
+                            .fill(
+                                LinearGradient(
+                                    colors: [.purple.opacity(0.2), .pink.opacity(0.2)],
+                                    startPoint: .topLeading,
+                                    endPoint: .bottomTrailing
+                                )
+                            )
+                            .frame(width: 80, height: 80)
+
+                        Image(systemName: "calendar.badge.clock")
+                            .font(.title)
+                            .foregroundStyle(
+                                LinearGradient(
+                                    colors: [.purple, .pink],
+                                    startPoint: .topLeading,
+                                    endPoint: .bottomTrailing
+                                )
+                            )
                     }
 
-                VStack {
-                    Spacer()
+                    // Text
+                    VStack(spacing: 10) {
+                        Text("Explore Your Mood History")
+                            .font(.title3.weight(.bold))
+                            .foregroundColor(textColor)
+                            .multilineTextAlignment(.center)
+
+                        Text("See your complete monthly journey. Track patterns and understand what shapes your days.")
+                            .font(.subheadline)
+                            .foregroundColor(textColor.opacity(0.7))
+                            .multilineTextAlignment(.center)
+                            .padding(.horizontal, 24)
+                    }
+
+                    // Subscribe button
                     Button {
                         showSubscriptionStore = true
                     } label: {
-                        Text(String(localized: "subscription_required_button"))
-                            .font(.headline)
-                            .foregroundColor(.white)
-                            .frame(maxWidth: .infinity)
-                            .padding()
-                            .background(RoundedRectangle(cornerRadius: 10).fill(Color.pink))
+                        HStack {
+                            Image(systemName: "calendar")
+                            Text("Unlock Full History")
+                        }
+                        .font(.headline.weight(.bold))
+                        .foregroundColor(.white)
+                        .frame(maxWidth: .infinity)
+                        .padding(.vertical, 14)
+                        .background(
+                            LinearGradient(
+                                colors: [.purple, .pink],
+                                startPoint: .leading,
+                                endPoint: .trailing
+                            )
+                        )
+                        .clipShape(RoundedRectangle(cornerRadius: 14))
                     }
-                    .padding()
+                    .padding(.horizontal, 24)
                 }
+                .padding(.vertical, 24)
+                .frame(maxWidth: .infinity)
+                .background(theme.currentTheme.bg)
+                .frame(maxHeight: .infinity, alignment: .bottom)
             } else if iapManager.shouldShowTrialWarning {
                 VStack {
                     Spacer()