fix: audit perbaikan NATS subject, worker spawn, frontend options, pipeline PDF output

Bug fixes:
1. NATS subject doubled prefix — gateway publish ke tools.tools.scan.*
   padahal workers subscribe ke tools.scan.*. Fix: pakai group() method
2. Worker subscriptions pake tokio::select! — cuma satu subscription
   yang diproses, sisanya di-cancel. Fix: ganti ke tokio::spawn + loop
3. WebSocket URL hardcoded ke localhost:3001 — gak jalan di prod.
   Fix: infer dari window.location atau env var
4. Frontend scan options hardcoded — user gak bisa atur OCR/enhance/format.
   Fix: interactive toggles, selects, slider
5. Frontend compress quality hardcoded — user gak bisa atur kualitas.
   Fix: quality range slider
6. Pipeline cuma output PNG — gak ada PDF/OCR.
   Fix: generate searchable PDF kalo tesseract feature enabled

Enhancements:
- Tool::group() method added — returns 'scan', 'image', 'pdf' dll
- Dockerfile: --features tesseract pas cargo build
- leptess OCR: proper API usage (set_image_from_mem, recognize, etc.)

Co-Authored-By: Kilo <kilo@kilo.ai>

backend/workers/src/nats/consumer.rs

@@ -53,18 +53,16 @@ impl JobConsumer {
             .await?;
         tracing::info!("Subscribed to tools.scheduler.cleanup");
 
-        let redis_clone = redis.clone();
-        let config_clone = config.clone();
+        // Process messages concurrently — use tokio::spawn so ALL run
+        tokio::spawn(Self::process_subscription(scan_sub, redis.clone(), config.clone()));
+        tokio::spawn(Self::process_subscription(image_sub, redis.clone(), config.clone()));
+        tokio::spawn(Self::process_subscription(pdf_sub, redis.clone(), config.clone()));
+        tokio::spawn(Self::process_cleanup(cleanup_sub, config.clone()));
 
-        // Process messages concurrently
-        tokio::select! {
-            _ = Self::process_subscription(scan_sub, redis.clone(), config.clone()) => {},
-            _ = Self::process_subscription(image_sub, redis.clone(), config.clone()) => {},
-            _ = Self::process_subscription(pdf_sub, redis.clone(), config.clone()) => {},
-            _ = Self::process_cleanup(cleanup_sub, config_clone) => {},
+        // Wait forever so the process doesn't exit
+        loop {
+            tokio::time::sleep(std::time::Duration::from_secs(3600)).await;
         }
-
-        Ok(())
     }
 
     /// Process messages from a NATS subscription.

backend/workers/src/nats/progress.rs

@@ -50,7 +50,7 @@ impl ProgressReporter {
             message: message.to_string(),
         };
 
-        let subject = format!("tools.{}.progress.{}", self.tool.subject_prefix(), self.job_id);
+        let subject = format!("tools.{}.progress.{}", self.tool.group(), self.job_id);
         if let Ok(payload) = serde_json::to_vec(&progress_msg) {
             let _ = self.nats.publish(subject, payload.into()).await;
         }