feat: Gemini AI (doc OCR + face match) + role-assignment endpoints

- GeminiService (integrations/gemini, @Global): extractDocument (OCR fields) + faceMatch; graceful if no GEMINI_API_KEY
- documents: face-match now real via Gemini; POST /admin/documents/:id/ocr extracts fields for CS auto-fill
- roles: PATCH /admin/users/:id/role (admin) + POST /platform/users/role (bootstrap via x-platform-secret)
- config: gemini + platform.secret; .env.example entries

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

apps/rider/android/build.gradle

@@ -0,0 +1,37 @@
+buildscript {
+    ext.kotlin_version = '1.9.10'
+    repositories {
+        google()
+        mavenCentral()
+    }
+
+    dependencies {
+        // START: FlutterFire Configuration
+//        classpath 'com.google.gms:google-services:4.4.2'
+//        // END: FlutterFire Configuration
+//        classpath 'com.android.tools.build:gradle:7.3.1'
+        classpath 'com.google.gms:google-services:4.3.15'
+        // END: FlutterFire Configuration
+        classpath 'com.android.tools.build:gradle:8.8.0'
+        classpath "org.jetbrains.kotlin:kotlin-gradle-plugin:$kotlin_version"
+    }
+}
+
+allprojects {
+    repositories {
+        google()
+        mavenCentral()
+    }
+}
+
+rootProject.buildDir = '../build'
+subprojects {
+    project.buildDir = "${rootProject.buildDir}/${project.name}"
+}
+subprojects {
+    project.evaluationDependsOn(':app')
+}
+
+tasks.register("clean", Delete) {
+    delete rootProject.buildDir
+}