Phase 1 MVP: gateway, CRUD handlers, frontend components

Backend:
- WebSocket gateway (hub, client, events) with fanout broadcast
- Server CRUD handlers (create, list, get, update, delete)
- Channel CRUD handlers (create, list, get, update, delete)
- Message CRUD handlers (list with cursor pagination, create, update, delete)
- cmd/migrate standalone migration CLI (up/down)
- cmd/server wired to all handlers + WebSocket + static file serving

Frontend:
- Zustand stores: auth, server, channel, message, websocket
- API client with fetch wrapper
- Terminal-styled components: Layout, LoginForm, ChatArea, ChannelList, ServerBar, MemberList
- React Router with login and main routes
- Gruvbox dark palette throughout

Ops:
- Docker Compose with app service (multi-stage build)
- Caddyfile with WebSocket upgrade support
- Makefile for common tasks

internal/gateway/events.go

@@ -0,0 +1,50 @@
+package gateway
+
+import "encoding/json"
+
+// Event type constants.
+const (
+	EventMessageCreate  = "MESSAGE_CREATE"
+	EventMessageUpdate  = "MESSAGE_UPDATE"
+	EventMessageDelete  = "MESSAGE_DELETE"
+	EventChannelCreate  = "CHANNEL_CREATE"
+	EventChannelUpdate  = "CHANNEL_UPDATE"
+	EventChannelDelete  = "CHANNEL_DELETE"
+	EventMemberAdd      = "SERVER_MEMBER_ADD"
+	EventMemberRemove   = "SERVER_MEMBER_REMOVE"
+	EventPresenceUpdate = "PRESENCE_UPDATE"
+	EventTypingStart    = "TYPING_START"
+)
+
+// Event represents a WebSocket event sent to clients.
+type Event struct {
+	Type string      `json:"type"`
+	Data interface{} `json:"data,omitempty"`
+}
+
+// MarshalJSON implements custom JSON marshaling for Event.
+func (e Event) MarshalJSON() ([]byte, error) {
+	type eventAlias struct {
+		Type string      `json:"type"`
+		Data interface{} `json:"data,omitempty"`
+	}
+	return json.Marshal(eventAlias{
+		Type: e.Type,
+		Data: e.Data,
+	})
+}
+
+// UnmarshalJSON implements custom JSON unmarshaling for Event.
+func (e *Event) UnmarshalJSON(data []byte) error {
+	type eventAlias struct {
+		Type string          `json:"type"`
+		Data json.RawMessage `json:"data,omitempty"`
+	}
+	var raw eventAlias
+	if err := json.Unmarshal(data, &raw); err != nil {
+		return err
+	}
+	e.Type = raw.Type
+	e.Data = raw.Data
+	return nil
+}