feat: add event bus, WS workspace isolation, and global store migration

- Add internal event bus (server/internal/events/) with synchronous
  pub/sub and panic isolation per listener
- Upgrade WebSocket Hub to workspace-scoped rooms with JWT auth
  and membership verification on connect
- Add 10 new WS event types (comment CRUD, inbox read/archive,
  agent create/delete, workspace/member events)
- Refactor all handlers and TaskService to publish events via Bus
  instead of direct Hub.Broadcast calls
- Add WS broadcast listener that routes events to correct workspace
- Frontend: WSClient sends token + workspace_id on connect with
  auto-reconnect refetch
- Frontend: centralized useRealtimeSync hook dispatches all WS
  events to global Zustand stores
- Migrate issues and inbox pages from local useState to global
  useIssueStore/useInboxStore
- Make store addIssue/addItem idempotent to prevent duplicates
- Remove dead packages/hooks/src/use-realtime.ts
- Add feature tracking files for 4 planned features

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

server/internal/handler/workspace.go

@@ -8,6 +8,7 @@ import (
 	"github.com/go-chi/chi/v5"
 	"github.com/jackc/pgx/v5/pgtype"
 	db "github.com/multica-ai/multica/server/pkg/db/generated"
+	"github.com/multica-ai/multica/server/pkg/protocol"
 )
 
 type WorkspaceResponse struct {
@@ -207,6 +208,9 @@ func (h *Handler) UpdateWorkspace(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	userID := requestUserID(r)
+	h.publish(protocol.EventWorkspaceUpdated, id, "member", userID, map[string]any{"workspace": workspaceToResponse(ws)})
+
 	writeJSON(w, http.StatusOK, workspaceToResponse(ws))
 }
 
@@ -355,6 +359,9 @@ func (h *Handler) CreateMember(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	userID := requestUserID(r)
+	h.publish(protocol.EventMemberAdded, workspaceID, "member", userID, map[string]any{"member": memberWithUserResponse(member, user)})
+
 	writeJSON(w, http.StatusCreated, memberWithUserResponse(member, user))
 }
 
@@ -463,6 +470,13 @@ func (h *Handler) DeleteMember(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	userID := requestUserID(r)
+	h.publish(protocol.EventMemberRemoved, workspaceID, "member", userID, map[string]any{
+		"member_id":    uuidToString(target.ID),
+		"workspace_id": workspaceID,
+		"user_id":      uuidToString(target.UserID),
+	})
+
 	w.WriteHeader(http.StatusNoContent)
 }
 
@@ -490,6 +504,13 @@ func (h *Handler) LeaveWorkspace(w http.ResponseWriter, r *http.Request) {
 		return
 	}
 
+	userID := requestUserID(r)
+	h.publish(protocol.EventMemberRemoved, workspaceID, "member", userID, map[string]any{
+		"member_id":    uuidToString(member.ID),
+		"workspace_id": workspaceID,
+		"user_id":      uuidToString(member.UserID),
+	})
+
 	w.WriteHeader(http.StatusNoContent)
 }