Add PostHog exception capture for crash reporting

Android: uncaught exception handler sends $exception events with stack
trace to PostHog, flushes before delegating to default handler.
iOS: NSSetUncaughtExceptionHandler captures crashes via PostHogSDK,
avoids @MainActor deadlock by calling SDK directly.
Common: captureException() available for non-fatal catches app-wide.
Platform stubs for jvm/js/wasmJs.

composeApp/src/androidMain/kotlin/com/tt/honeyDue/MainActivity.kt

@@ -80,6 +80,9 @@ class MainActivity : FragmentActivity(), SingletonImageLoader.Factory {
         // Initialize PostHog Analytics
         PostHogAnalytics.initialize(application, debug = true) // Set debug=false for release
 
+        // Install uncaught exception handler to capture crashes to PostHog
+        PostHogAnalytics.setupExceptionHandler()
+
         // Handle deep link, notification navigation, and file import from intent
         handleDeepLink(intent)
         handleNotificationNavigation(intent)

composeApp/src/androidMain/kotlin/com/tt/honeyDue/analytics/PostHogAnalytics.android.kt

@@ -1,6 +1,7 @@
 package com.tt.honeyDue.analytics
 
 import android.app.Application
+import android.util.Log
 import com.posthog.PostHog
 import com.posthog.android.PostHogAndroid
 import com.posthog.android.PostHogAndroidConfig
@@ -13,6 +14,8 @@ actual object PostHogAnalytics {
     private const val API_KEY = "YOUR_POSTHOG_API_KEY"
     private const val HOST = "https://us.i.posthog.com"
 
+    private const val TAG = "PostHogAnalytics"
+
     private var isInitialized = false
     private var application: Application? = null
 
@@ -57,6 +60,28 @@ actual object PostHogAnalytics {
         PostHog.capture(event, properties = properties)
     }
 
+    /**
+     * Capture an exception/crash as a PostHog `$exception` event.
+     * Uses PostHog's standard exception property names so exceptions
+     * appear correctly in the PostHog Errors dashboard.
+     */
+    actual fun captureException(throwable: Throwable, properties: Map<String, Any>?) {
+        if (!isInitialized) return
+        try {
+            val exceptionProps = mutableMapOf<String, Any>(
+                "\$exception_type" to (throwable::class.simpleName ?: "Unknown"),
+                "\$exception_message" to (throwable.message ?: "No message"),
+                "\$exception_stack_trace_raw" to throwable.stackTraceToString()
+            )
+            if (properties != null) {
+                exceptionProps.putAll(properties)
+            }
+            PostHog.capture("\$exception", properties = exceptionProps)
+        } catch (e: Exception) {
+            Log.e(TAG, "Failed to capture exception to PostHog", e)
+        }
+    }
+
     actual fun screen(screenName: String, properties: Map<String, Any>?) {
         if (!isInitialized) return
         PostHog.screen(screenName, properties = properties)
@@ -71,4 +96,36 @@ actual object PostHogAnalytics {
         if (!isInitialized) return
         PostHog.flush()
     }
+
+    /**
+     * Install an uncaught exception handler that captures crashes to PostHog
+     * before delegating to the default handler (which shows the crash dialog).
+     * Call this after initialize() in MainActivity.onCreate().
+     */
+    actual fun setupExceptionHandler() {
+        if (!isInitialized) return
+
+        val defaultHandler = Thread.getDefaultUncaughtExceptionHandler()
+        Thread.setDefaultUncaughtExceptionHandler { thread, throwable ->
+            try {
+                PostHog.capture(
+                    event = "\$exception",
+                    properties = mapOf(
+                        "\$exception_type" to (throwable::class.simpleName ?: "Unknown"),
+                        "\$exception_message" to (throwable.message ?: "No message"),
+                        "\$exception_stack_trace_raw" to throwable.stackTraceToString(),
+                        "\$exception_thread" to thread.name,
+                        "\$exception_is_fatal" to true
+                    )
+                )
+                // Flush to ensure the event is sent before the process dies
+                PostHog.flush()
+            } catch (_: Exception) {
+                // Don't let our crash handler crash
+            }
+            // Call the default handler so the system crash dialog still appears
+            defaultHandler?.uncaughtException(thread, throwable)
+        }
+        Log.d(TAG, "Uncaught exception handler installed")
+    }
 }