feat: batch job pulling for native workers

Reduce DB polling overhead for native workers by batch-fetching jobs
server-side and serving them from an in-memory buffer via HTTP.

- Add batch_pull() in windmill-queue: single SELECT...FOR UPDATE SKIP LOCKED LIMIT N
- Add batch pull SQL helpers (make_batch_pull_query, format_batch_pull_query)
- OSS stubs for agent-workers accept batch_buffer parameter (4-tuple return)
- Native workers self-sign JWT and pull jobs via HTTP when co-located with server
- Add uses_batch_http_pull column to worker_ping for server-side tracking
- Worker pull loop: HTTP batch pull when client available, SQL otherwise

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

backend/windmill-api/src/lib.rs

@@ -422,12 +422,16 @@ pub async fn run_server(
     };
 
     #[cfg(feature = "agent_worker_server")]
-    let (agent_workers_router, agent_workers_bg_processor, agent_workers_job_completed_tx) =
-        if server_mode {
-            windmill_api_agent_workers::workspaced_service(db.clone(), _base_internal_url.clone())
-        } else {
-            (Router::new(), vec![], None)
-        };
+    let (
+        agent_workers_router,
+        agent_workers_bg_processor,
+        agent_workers_job_completed_tx,
+        batch_buffer,
+    ) = if server_mode {
+        windmill_api_agent_workers::workspaced_service(db.clone(), _base_internal_url.clone())
+    } else {
+        (Router::new(), vec![], None, None)
+    };
 
     #[cfg(feature = "agent_worker_server")]
     let agent_cache = Arc::new(AgentCache::new());
@@ -612,6 +616,7 @@ pub async fn run_server(
                         {
                             windmill_api_agent_workers::global_service(
                                 agent_workers_job_completed_tx,
+                                batch_buffer.clone(),
                             )
                             .layer(Extension(agent_cache.clone()))
                         } else {