[management, proxy] Management-owned LLM pricing: file-backed defaults +

operator prices, delivered via cost_meter middleware config

  Operator-pinned model prices (ProviderModel.InputPer1k/OutputPer1k) were
  stored and round-tripped through the API but never consumed for billing:
  the proxy priced exclusively from a defaults_pricing.yaml embedded in
  its binary. Any model outside that file recorded $0 spend, price changes
  required a proxy release, and the catalog and the YAML were two
  hand-synced copies of the same rates, guarded only by a manually
  maintained coverage list that had already drifted.

proxy/server.go

@@ -246,10 +246,6 @@ type Server struct {
 	// in processMappings before the receive loop reconnects to resync.
 	// Zero uses defaultMappingBatchWatchdog.
 	MappingBatchWatchdog time.Duration
-	// MiddlewareDataDir is the base directory the middleware system uses to
-	// resolve file-backed configuration (e.g. the cost_meter pricing table).
-	// Empty means any middleware that requires a file fails at configure time.
-	MiddlewareDataDir string
 	// MiddlewareCaptureBudgetBytes overrides the proxy-wide in-flight capture
 	// budget passed to middleware.NewManager. Zero or negative values fall
 	// back to defaultMiddlewareCaptureBudgetBytes (256 MiB).
@@ -2093,7 +2089,7 @@ func (s *Server) initMiddlewareManager(ctx context.Context) error {
 		return fmt.Errorf("middleware manager requires metrics bundle")
 	}
 	otelMeter := s.meter.Meter()
-	mwbuiltin.Configure(ctx, s.MiddlewareDataDir, otelMeter, s.Logger, s.mgmtClient)
+	mwbuiltin.Configure(ctx, otelMeter, s.Logger, s.mgmtClient)
 
 	mwMetrics, err := middleware.NewMetrics(otelMeter)
 	if err != nil {