Store SCUM facts in typed platform tables

Run pushes typed SCUM facts through POST /api/v1/run/scum/facts, but the
production router rejected that path before the signature middleware because
runServiceRequest listed individual Run channel prefixes, and MySQL kept SCUM
rows inside the whole metadata snapshot instead of platform tables.

- /api/v1/run/ is now the signed machine channel space while
  /api/v1/run/endpoints keeps normal bearer/admin authorization.
- MySQL gets real scum_user, scum_user_trajectory, scum_vehicle,
  scum_vehicle_trajectory and scum_vehicle_lock tables with parameterized
  per-row repositories instead of full snapshot rewrites. Snapshot-shaped
  tables from the unreleased interim build are replaced, and SCUM rows still
  inside a metadata snapshot are migrated once.
- Facts ingest verifies the target server plugin type and converges stale
  online users to offline after SCUMUserOfflineAfter.
- The plugin page and browser read one bounded /scum/surface response instead
  of five list calls per refresh.

Call-count budget for one server: per 5s facts batch, one SELECT plus one
INSERT/UPDATE per reported user and vehicle, one INSERT per moved trajectory
sample or new lock row, one bounded stale-user SELECT, and a trajectory
retention DELETE at most once per hour. One browser refresh issues one surface
request every 15s instead of five list requests.

platform/domain/scum.go

@@ -45,7 +45,10 @@ type SCUMUserFilter struct {
 	SteamID          string
 	Online           *bool
 	ChangedAfter     time.Time
-	Limit            int
+	// StaleBefore matches users whose latest activity is older than the given
+	// instant. It backs the offline convergence query for stale online users.
+	StaleBefore time.Time
+	Limit       int
 }
 
 type SCUMUserTrajectory struct {
@@ -137,6 +140,14 @@ type SCUMVehicleLockFilter struct {
 	Limit            int
 }
 
+type SCUMSurface struct {
+	Users               []SCUMUser
+	Vehicles            []SCUMVehicle
+	UserTrajectories    []SCUMUserTrajectory
+	VehicleTrajectories []SCUMVehicleTrajectory
+	VehicleLocks        []SCUMVehicleLock
+}
+
 type SCUMFactIngest struct {
 	RunEndpointID    string
 	SessionToken     string