Add PostHog analytics integration for Android and iOS

Implement comprehensive analytics tracking across both platforms:

Android (Kotlin):
- Add PostHog SDK dependency and initialization in MainActivity
- Create expect/actual pattern for cross-platform analytics (commonMain/androidMain/iosMain/jvmMain/jsMain/wasmJsMain)
- Track screen views: registration, login, residences, tasks, contractors, documents, notifications, profile
- Track key events: user_registered, user_signed_in, residence_created, task_created, contractor_created, document_created
- Track paywall events: contractor_paywall_shown, documents_paywall_shown
- Track sharing events: residence_shared, contractor_shared
- Track theme_changed event

iOS (Swift):
- Add PostHog iOS SDK via SPM
- Create PostHogAnalytics wrapper and AnalyticsEvents constants
- Initialize SDK in iOSApp with session replay support
- Track same screen views and events as Android
- Track user identification after login/registration

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

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

composeApp/src/androidMain/kotlin/com/example/casera/MainActivity.kt

@@ -37,6 +37,7 @@ import com.example.casera.data.DataManager
 import com.example.casera.data.PersistenceManager
 import com.example.casera.models.CaseraPackageType
 import com.example.casera.models.detectCaseraPackageType
+import com.example.casera.analytics.PostHogAnalytics
 import kotlinx.coroutines.launch
 
 class MainActivity : ComponentActivity(), SingletonImageLoader.Factory {
@@ -71,6 +72,9 @@ class MainActivity : ComponentActivity(), SingletonImageLoader.Factory {
         // Initialize BillingManager for subscription management
         billingManager = BillingManager.getInstance(applicationContext)
 
+        // Initialize PostHog Analytics
+        PostHogAnalytics.initialize(application, debug = true) // Set debug=false for release
+
         // Handle deep link, notification navigation, and file import from intent
         handleDeepLink(intent)
         handleNotificationNavigation(intent)

composeApp/src/androidMain/kotlin/com/example/casera/analytics/PostHogAnalytics.android.kt

@@ -0,0 +1,74 @@
+package com.example.casera.analytics
+
+import android.app.Application
+import com.posthog.PostHog
+import com.posthog.android.PostHogAndroid
+import com.posthog.android.PostHogAndroidConfig
+
+/**
+ * Android implementation of PostHog Analytics.
+ */
+actual object PostHogAnalytics {
+    // TODO: Replace with your actual PostHog API key
+    private const val API_KEY = "YOUR_POSTHOG_API_KEY"
+    private const val HOST = "https://us.i.posthog.com"
+
+    private var isInitialized = false
+    private var application: Application? = null
+
+    /**
+     * Initialize PostHog SDK with Application context.
+     * Call this in MainActivity.onCreate() before using other methods.
+     */
+    fun initialize(application: Application, debug: Boolean = false) {
+        if (isInitialized) return
+        this.application = application
+
+        val config = PostHogAndroidConfig(API_KEY, HOST).apply {
+            captureScreenViews = false // We'll track screens manually
+            captureApplicationLifecycleEvents = true
+            captureDeepLinks = true
+            this.debug = debug
+
+            // Session Replay
+            sessionReplay = true
+            sessionReplayConfig.maskAllTextInputs = true
+            sessionReplayConfig.maskAllImages = false
+        }
+
+        PostHogAndroid.setup(application, config)
+        isInitialized = true
+    }
+
+    /**
+     * Initialize from common code (no-op on Android, use initialize(Application) instead)
+     */
+    actual fun initialize() {
+        // No-op - Android requires Application context, use initialize(Application) instead
+    }
+
+    actual fun identify(userId: String, properties: Map<String, Any>?) {
+        if (!isInitialized) return
+        PostHog.identify(userId, userProperties = properties)
+    }
+
+    actual fun capture(event: String, properties: Map<String, Any>?) {
+        if (!isInitialized) return
+        PostHog.capture(event, properties = properties)
+    }
+
+    actual fun screen(screenName: String, properties: Map<String, Any>?) {
+        if (!isInitialized) return
+        PostHog.screen(screenName, properties = properties)
+    }
+
+    actual fun reset() {
+        if (!isInitialized) return
+        PostHog.reset()
+    }
+
+    actual fun flush() {
+        if (!isInitialized) return
+        PostHog.flush()
+    }
+}

composeApp/src/androidMain/kotlin/com/example/casera/platform/ContractorSharing.android.kt

@@ -5,6 +5,8 @@ import androidx.compose.runtime.Composable
 import androidx.compose.ui.platform.LocalContext
 import com.example.casera.models.Contractor
 import com.example.casera.sharing.ContractorSharingManager
+import com.example.casera.analytics.PostHogAnalytics
+import com.example.casera.analytics.AnalyticsEvents
 
 @Composable
 actual fun rememberShareContractor(): (Contractor) -> Unit {
@@ -13,6 +15,8 @@ actual fun rememberShareContractor(): (Contractor) -> Unit {
     return { contractor: Contractor ->
         val intent = ContractorSharingManager.createShareIntent(context, contractor)
         if (intent != null) {
+            // Track contractor shared event
+            PostHogAnalytics.capture(AnalyticsEvents.CONTRACTOR_SHARED)
             context.startActivity(Intent.createChooser(intent, "Share Contractor"))
         }
     }

composeApp/src/androidMain/kotlin/com/example/casera/platform/ResidenceSharing.android.kt

@@ -10,6 +10,8 @@ import androidx.compose.runtime.setValue
 import androidx.compose.ui.platform.LocalContext
 import com.example.casera.models.Residence
 import com.example.casera.sharing.ResidenceSharingManager
+import com.example.casera.analytics.PostHogAnalytics
+import com.example.casera.analytics.AnalyticsEvents
 import kotlinx.coroutines.launch
 
 @Composable
@@ -25,6 +27,11 @@ actual fun rememberShareResidence(): Pair<ResidenceSharingState, (Residence) ->
             val intent = ResidenceSharingManager.createShareIntent(context, residence)
             if (intent != null) {
                 state = ResidenceSharingState(isLoading = false)
+                // Track residence shared event
+                PostHogAnalytics.capture(
+                    AnalyticsEvents.RESIDENCE_SHARED,
+                    mapOf("method" to "file")
+                )
                 context.startActivity(Intent.createChooser(intent, "Share Residence"))
             } else {
                 state = ResidenceSharingState(