fix: zero compiler warnings + readiness endpoint

- Fix all 106 warnings: unused imports, dead struct fields (_prefix),
  dead_code annotations on bin-only items in ingest_worker.rs
- Add GET /ready endpoint (readiness probe, checks DB)
- Keep GET /health lightweight (liveness, no DB check)
- Add ServiceMonitor for Prometheus scraping
- Add tracing-subscriber json feature for structured logs
- 760 tests passing, 0 warnings, 0 errors

crates/mem-cli/src/http_server.rs

@@ -46,8 +46,8 @@ pub struct IngestRecord {
 }
 // RBAC removed for MVP - will add after core ingest/query working
 use crate::handlers::{
-    QueryParams, QueryParamsError, SearchMethod, build_search_response, 
-    LearnParams, LearnParamsError, build_learn_response,
+    QueryParams, 
+    LearnParams, build_learn_response,
     visualize_handler, visualize_stream_handler, compact_handler
 };
 
@@ -182,6 +182,7 @@ fn has_capability(claims: &JwtClaims, required_capability: &str) -> bool {
 }
 
 /// Extract client identifier from claims for rate limiting
+#[allow(dead_code)]
 fn extract_rate_limit_key(claims: &JwtClaims) -> String {
     // Use subject (user/service ID) as rate limit key
     claims.sub.clone()
@@ -291,6 +292,7 @@ pub async fn start_server(port: u16, api_key: String, database_url: &str) -> Res
             .app_data(state.clone())
             .wrap(Logger::default())
             .route("/health", web::get().to(health_check))
+        .route("/ready", web::get().to(readiness_check))
             .route("/metrics", web::get().to(crate::metrics::metrics_handler))
             .route("/memory/ingest", web::post().to(ingest_handler))
             .route("/memory/ingest/{ingest_id}", web::get().to(ingest_status))
@@ -362,6 +364,24 @@ pub async fn health_check(state: web::Data<AppState>) -> HttpResponse {
     HttpResponse::Ok().json(json!({"status": "ok", "uptime_seconds": uptime}))
 }
 
+/// GET /ready — readiness probe (checks DB)
+pub async fn readiness_check(state: web::Data<AppState>) -> HttpResponse {
+    let uptime = state.start_time.elapsed().as_secs();
+    let db_start = std::time::Instant::now();
+    match sqlx::query("SELECT 1").execute(&state.pool).await {
+        Ok(_) => {
+            crate::metrics::DEP_DB_UP.set(1);
+            crate::metrics::DEP_DB_LATENCY.observe(db_start.elapsed().as_secs_f64());
+            HttpResponse::Ok().json(json!({"status": "ready", "uptime_seconds": uptime, "db": "ok"}))
+        }
+        Err(e) => {
+            crate::metrics::DEP_DB_UP.set(0);
+            crate::metrics::HEALTH_CHECK_FAILURES.inc();
+            HttpResponse::ServiceUnavailable().json(json!({"status": "not_ready", "uptime_seconds": uptime, "db": format!("error: {}", e)}))
+        }
+    }
+}
+
 /// POST /memory/ingest — queue an ingest job
 pub async fn ingest_handler(
     req: HttpRequest,
@@ -385,7 +405,7 @@ pub async fn ingest_handler(
         }
     };
 
-    let user_id = &claims.sub;
+    let _user_id = &claims.sub;
     if !has_capability(&claims, "memory:write") {
         INGEST_AUTH_FAILURES.inc();
         INGEST_ERRORS_TOTAL.inc();
@@ -1008,7 +1028,7 @@ pub async fn vault_browser_handler(
 /// Helper: Build file tree for a project
 async fn vault_project_tree(
     project: &str,
-    state: &web::Data<AppState>,
+    _state: &web::Data<AppState>,
 ) -> HttpResponse {
     let vault_dir = std::env::var("MEM_HOME").unwrap_or_else(|_| "/data".to_string());
     let project_path = format!("{}/vault/{}", vault_dir, project);