fix(server): harden job eviction and worker against missing job id

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

server/jobs.py

@@ -30,6 +30,7 @@ def _touch(job: "Job", **changes):
 
 
 def _evict_if_needed():
+    # Post-condition: len(JOBS) <= _MAX_JOBS (evicts oldest overflow entries).
     if len(JOBS) <= _MAX_JOBS:
         return
     for jid in sorted(JOBS, key=lambda j: JOBS[j].created_at)[: len(JOBS) - _MAX_JOBS]:
@@ -50,7 +51,9 @@ def get_job(job_id: str) -> Optional["Job"]:
 def run_job(job_id: str, fn: Callable[[], dict], done_message: str,
             fail_message: str = "Something went wrong while fetching.") -> None:
     def _task():
-        job = JOBS[job_id]
+        job = JOBS.get(job_id)
+        if job is None:
+            return
         _touch(job, status="running")
         try:
             result = fn()