fix: Add missing indices to PilotAgentsDB and JobDB

[chrisburr]

Two hot-path queries are doing full table scans due to missing indices:

1. PilotAgentsDB — SiteDirector.countPilots() filters on (DestinationSite, Queue, Status) every scheduling cycle. The existing Statuskey index is (GridSite, DestinationSite, Status) which doesn't cover Queue and has the wrong leading column for this query. A composite idx_dest_queue_status index is added.

2. JobDB — WorkflowTasks.updateTransformationReservedTasks() calls getJobs({"JobName": jobNames}), which does SELECT JobID FROM Jobs WHERE JobName IN (...). JobName had no index at all, causing a full table scan. Also hit by dstat.py and the REST API. A JobName index is added.

Both are pure schema changes to the .sql definition files. For existing deployments the schema change only takes effect on newly created tables (__initializeDB skips tables that already exist). Production DBs need a one-off ALTER TABLE to add the indices.

BEGINRELEASENOTES
*WorkloadManagement
FIX: Add composite (DestinationSite, Queue, Status) index to PilotAgents table for SiteDirector.countPilots()
FIX: Add JobName index to Jobs table for TransformationSystem and monitoring lookups

*Deployment
CHANGE: USE JobDB; ALTER TABLE Jobs ADD INDEX JobName (JobName), ALGORITHM=INPLACE, LOCK=NONE;
CHANGE: USE PilotAgentsDB; ALTER Table PilotAgents ADD INDEX idx_dest_queue_status (DestinationSite,Queue,Status), ALGORITHM=INPLACE, LOCK=NONE;

ENDRELEASENOTES