Wire up FCM push notification service

- ClippyFCMService: Receives FCM data messages, routes to TTS pipeline
- FCMTokenManager: Stores FCM token in Matrix account data for n8n
- Enable Google Services plugin and Firebase dependencies
- Add FCM service to AndroidManifest.xml
- Register FCM token on app init in ClippySession and SetupActivity

Token stored at: /_matrix/client/v3/user/@clippyauto:hobbs.farm/account_data/farm.hobbs.clippy.fcm_token

Co-authored-by: Spirit <spirit@hobbs.farm>

app/build.gradle.kts

@@ -2,8 +2,7 @@ plugins {
     id("com.android.application")
     id("org.jetbrains.kotlin.android")
     id("org.jetbrains.kotlin.plugin.serialization")
-    // Firebase deferred to Sprint 2
-    // id("com.google.gms.google-services")
+    id("com.google.gms.google-services")
 }
 
 android {
@@ -40,9 +39,9 @@ dependencies {
     implementation("androidx.car.app:app:1.7.0")
     implementation("androidx.car.app:app-projected:1.7.0")
 
-    // Firebase Cloud Messaging — Sprint 2
-    // implementation(platform("com.google.firebase:firebase-bom:33.9.0"))
-    // implementation("com.google.firebase:firebase-messaging-ktx")
+    // Firebase Cloud Messaging
+    implementation(platform("com.google.firebase:firebase-bom:33.1.0"))
+    implementation("com.google.firebase:firebase-messaging-ktx")
 
     // HTTP client for Matrix REST API
     implementation("io.ktor:ktor-client-okhttp:3.0.3")
@@ -51,6 +50,7 @@ dependencies {
 
     // Coroutines
     implementation("org.jetbrains.kotlinx:kotlinx-coroutines-android:1.9.0")
+    implementation("org.jetbrains.kotlinx:kotlinx-coroutines-play-services:1.7.3")
 
     // Lifecycle
     implementation("androidx.lifecycle:lifecycle-runtime-ktx:2.8.7")