feat: affiche les versions API, Indexer et Backoffice dans About

- Endpoint GET /version sur l'indexer (sans auth)
- Le backoffice fetch la version indexer directement (INDEXER_BASE_URL)
- Grille 3 colonnes avec les 3 versions

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/indexer/src/api.rs

@@ -7,6 +7,12 @@ pub async fn health() -> &'static str {
     "ok"
 }
 
+pub async fn version() -> Json<serde_json::Value> {
+    Json(serde_json::json!({
+        "indexer": env!("CARGO_PKG_VERSION"),
+    }))
+}
+
 pub async fn ready(State(state): State<AppState>) -> Result<Json<serde_json::Value>, StatusCode> {
     sqlx::query("SELECT 1")
         .execute(&state.pool)

apps/indexer/src/main.rs

@@ -36,6 +36,7 @@ async fn async_main() -> anyhow::Result<()> {
 
     let app = Router::new()
         .route("/health", get(api::health))
+        .route("/version", get(api::version))
         .route("/ready", get(api::ready))
         .with_state(state.clone());