Make Redis collaborators optional on RqueueBeanProvider and RqueueMetrics

Both classes used to mandate Redis-shaped beans through @Autowired
defaults. With those beans now gated behind RedisBackendCondition the
NATS backend path failed Spring DI:

  - RqueueBeanProvider.{rqueueMessageMetadataService, rqueueSystemConfigDao,
    rqueueJobDao, rqueueLockManager} switched to @Autowired(required=false).
    The bean provider already exposes setters and tolerates nulls in the
    Redis-only consumer paths.
  - RqueueMetrics.rqueueStringDao switched to @Autowired(required=false);
    the size() helper short-circuits to 0 when no Redis is wired so the
    micrometer gauges still register but report zero on NATS deployments.

Assisted-By: Claude Code

Author: sonus21

.claude/scheduled_tasks.lock

@@ -0,0 +1 @@
+{"sessionId":"dc2dc485-0866-434b-8dc1-34030f338e1f","pid":58262,"procStart":"Thu Apr 30 14:08:59 2026","acquiredAt":1777558217212}

.claude/worktrees/agent-a2fb0621f48f3b0e0

@@ -0,0 +1 @@
+Subproject commit fb3878bef95eb65f55d68c86565accc03218375d

.claude/worktrees/agent-a36dfbbe1dfef510f

@@ -0,0 +1 @@
+Subproject commit 434c42cbdd3455e3f6eab0b17483d97128b21d19

.claude/worktrees/agent-aafca1f302abb9516

@@ -0,0 +1 @@
+Subproject commit 764bd5868feb27e80084cf298c4ce6cadd39af31

.claude/worktrees/agent-adac06884be8e97cb

@@ -0,0 +1 @@
+Subproject commit 436395a92b893a6adc2ed94176b56489cdfe333b

rqueue-core/src/main/java/com/github/sonus21/rqueue/core/RqueueBeanProvider.java

@@ -35,13 +35,14 @@
 @Setter
 public class RqueueBeanProvider {
 
-  @Autowired
+  // Redis-only collaborators — absent on the NATS backend path; consumers must null-check.
+  @Autowired(required = false)
   private RqueueMessageMetadataService rqueueMessageMetadataService;
 
-  @Autowired
+  @Autowired(required = false)
   private RqueueSystemConfigDao rqueueSystemConfigDao;
 
-  @Autowired
+  @Autowired(required = false)
   private RqueueJobDao rqueueJobDao;
 
   @Autowired
@@ -50,7 +51,7 @@ public class RqueueBeanProvider {
   @Autowired
   private ApplicationEventPublisher applicationEventPublisher;
 
-  @Autowired
+  @Autowired(required = false)
   private RqueueLockManager rqueueLockManager;
 
   @Autowired(required = false)

rqueue-core/src/main/java/com/github/sonus21/rqueue/metrics/RqueueMetrics.java

@@ -48,14 +48,19 @@ public class RqueueMetrics implements RqueueMetricsRegistry {
   @Autowired
   private MeterRegistry meterRegistry;
 
-  @Autowired
+  // Redis-only — null when rqueue.backend=nats; size() returns 0 in that case.
+  @Autowired(required = false)
   private RqueueStringDao rqueueStringDao;
 
   public RqueueMetrics(QueueCounter queueCounter) {
     this.queueCounter = queueCounter;
   }
 
   private long size(String name, boolean isZset) {
+    if (rqueueStringDao == null) {
+      // No Redis available (e.g. rqueue.backend=nats); these metrics are Redis-shaped.
+      return 0;
+    }
     Long val;
     if (!isZset) {
       val = rqueueStringDao.getListSize(name);