feat(federation): add dolt sql-server mode for daemon (bd-wkumz.2)

Add --federation flag to bd daemon start that runs dolt sql-server
instead of the embedded driver. Enables multi-writer support and
exposes remotesapi on port 8080 for peer-to-peer push/pull.

Changes:
- Add --federation flag to daemon start command
- Create dolt server manager (internal/storage/dolt/server.go)
- Update DoltStore to support server mode via MySQL protocol
- Integrate server lifecycle into daemon (auto-start/stop)
- Add tests for server management and server mode connections

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

internal/storage/factory/factory.go

@@ -26,6 +26,11 @@ func RegisterBackend(name string, factory BackendFactory) {
 type Options struct {
 	ReadOnly    bool
 	LockTimeout time.Duration
+
+	// Dolt server mode options (federation)
+	ServerMode bool   // Connect to dolt sql-server instead of embedded
+	ServerHost string // Server host (default: 127.0.0.1)
+	ServerPort int    // Server port (default: 3306)
 }
 
 // New creates a storage backend based on the backend type.

internal/storage/factory/factory_dolt.go

@@ -41,6 +41,12 @@ func init() {
 			fmt.Fprintf(os.Stderr, "\n  Dolt database ready\n")
 		}
 
-		return dolt.New(ctx, &dolt.Config{Path: path, ReadOnly: opts.ReadOnly})
+		return dolt.New(ctx, &dolt.Config{
+			Path:       path,
+			ReadOnly:   opts.ReadOnly,
+			ServerMode: opts.ServerMode,
+			ServerHost: opts.ServerHost,
+			ServerPort: opts.ServerPort,
+		})
 	})
 }