Add stale recovery to tracker mapping worker

The tracker-mapping worker clears mapping_requested_at at claim time, so
a crash or hard failure between Process phases left the pattern dequeued,
unmapped, and with nothing to re-trigger it. Only an incidental sibling
remap could rescue it, so a lone pattern could stay stranded forever.

Implement the worker.StaleRecoverer interface, mirroring the enrichment
worker. ResetStaleMappings re-arms rows that were claimed but never
assigned a catalog row (common_tracker_pattern_id IS NULL) once idle past
a configurable window; a successful Process always assigns one via the
unmatched fallback, so the predicate cleanly detects interrupted runs and
self-heals after a single pass. ClearMappingRequestedAt now bumps
updated_at so the stale clock starts at claim time and the sweep never
recycles an in-flight claim.

Plumb a StaleAfter knob (default 600s) through the config struct, builder
env var, probod wiring, and Helm templates.

Signed-off-by: Émile Ré <emile@probo.com>

pkg/probodconfig/llm_config.go

@@ -48,6 +48,7 @@ type (
 	TrackerMappingWorkerConfig struct {
 		Interval       int `json:"interval"` // seconds between polls
 		MaxConcurrency int `json:"max-concurrency"`
+		StaleAfter     int `json:"stale-after"`   // seconds before a claim is recycled
 		AgentTimeout   int `json:"agent-timeout"` // seconds, single agent run
 		AgentMaxTurns  int `json:"agent-max-turns"`
 	}