fix: remove duplicate bridge watchers, expose Handler for Base mount

- Remove pkg/bridge/ (btc_watcher + orchestrator) — bridge/opnet-watcher
  is the single source of truth for chain watching per CTO directive
- Add Handler() to API server for mounting on Hanzo Base
- MPC is signing-only; bridge is the control plane

go.work.sum

@@ -690,6 +690,7 @@ github.com/tilinna/z85 v1.0.0/go.mod h1:EfpFU/DUY4ddEy6CRvk2l+UQNEzHbh+bqBQS+04N
 github.com/tinylib/msgp v1.1.8/go.mod h1:qkpG+2ldGg4xRFmx+jfTvZPxfGFhi64BcnL9vkCm/Tw=
 github.com/tklauser/go-sysconf v0.3.16/go.mod h1:/qNL9xxDhc7tx3HSRsLWNnuzbVfh3e7gh/BmM179nYI=
 github.com/tklauser/numcpus v0.11.0/go.mod h1:z+LwcLq54uWZTX0u/bGobaV34u6V7KNlTZejzM6/3MQ=
+github.com/urfave/cli v1.22.17 h1:SYzXoiPfQjHBbkYxbew5prZHS1TOLT3ierW8SYLqtVQ=
 github.com/urfave/cli v1.22.17/go.mod h1:b0ht0aqgH/6pBYzzxURyrM4xXNgsoT/n2ZzwQiEhNVo=
 github.com/urfave/cli/v2 v2.27.7/go.mod h1:CyNAG/xg+iAOg0N4MPGZqVmv2rCoP267496AOXUZjA4=
 github.com/urfave/cli/v3 v3.6.2/go.mod h1:ysVLtOEmg2tOy6PknnYVhDoouyC/6N42TMeoMzskhso=

pkg/api/server.go

@@ -405,6 +405,11 @@ func (s *Server) SetTradeApproval(notifier custody.PushNotifier) {
 	s.tradeApproval = custody.NewTradeApprovalService(s.db.ORM, notifier)
 }
 
+// Handler returns the underlying http.Handler for mounting on external servers (e.g. Hanzo Base).
+func (s *Server) Handler() http.Handler {
+	return s.router
+}
+
 // Shutdown gracefully drains connections and stops the server.
 func (s *Server) Shutdown(ctx context.Context) error {
 	return s.server.Shutdown(ctx)