feat: server members API + member list in sidebar + fix chat input

Backend:
- Add GET /api/v1/servers/{serverID}/members endpoint
- Wire MemberHandler routes in main.go

Frontend:
- Create member store (fetchMembers by server ID)
- MemberList now fetches members from API instead of empty props
- ChatArea: show channel name instead of ID, add error display,
  add flex-1 + min-w-0 to input for proper sizing, error handling
  on sendMessage

internal/server/members.go

@@ -0,0 +1,76 @@
+package server
+
+import (
+	"database/sql"
+	"encoding/json"
+	"net/http"
+
+	"git.dustin.coffee/hobokenchicken/dumpsterChat/internal/middleware"
+	"github.com/go-chi/chi/v5"
+)
+
+type MemberHandler struct {
+	db *sql.DB
+}
+
+func NewMemberHandler(db *sql.DB) *MemberHandler {
+	return &MemberHandler{db: db}
+}
+
+func (h *MemberHandler) RegisterRoutes(r chi.Router) {
+	r.Get("/members", h.ListMembers)
+}
+
+type memberResponse struct {
+	ID          string `json:"id"`
+	Username    string `json:"username"`
+	DisplayName string `json:"display_name"`
+	Avatar      string `json:"avatar"`
+	Status      string `json:"status"`
+	StatusText  string `json:"status_text"`
+}
+
+func (h *MemberHandler) ListMembers(w http.ResponseWriter, r *http.Request) {
+	userID, ok := middleware.UserIDFromContext(r.Context())
+	if !ok {
+		http.Error(w, `{"error":"unauthorized"}`, http.StatusUnauthorized)
+		return
+	}
+
+	serverID := chi.URLParam(r, "serverID")
+
+	// Verify the caller is a member
+	var exists bool
+	err := h.db.QueryRowContext(r.Context(),
+		`SELECT EXISTS(SELECT 1 FROM members WHERE user_id = $1 AND server_id = $2)`,
+		userID, serverID).Scan(&exists)
+	if err != nil || !exists {
+		http.Error(w, `{"error":"not a member"}`, http.StatusForbidden)
+		return
+	}
+
+	rows, err := h.db.QueryContext(r.Context(), `
+		SELECT u.id, u.username, u.display_name, COALESCE(u.avatar, ""), u.status, COALESCE(u.status_text, "")
+		FROM members m
+		JOIN users u ON u.id = m.user_id
+		WHERE m.server_id = $1
+		ORDER BY u.username
+	`, serverID)
+	if err != nil {
+		http.Error(w, `{"error":"server error"}`, http.StatusInternalServerError)
+		return
+	}
+	defer rows.Close()
+
+	members := make([]memberResponse, 0)
+	for rows.Next() {
+		var m memberResponse
+		if err := rows.Scan(&m.ID, &m.Username, &m.DisplayName, &m.Avatar, &m.Status, &m.StatusText); err != nil {
+			continue
+		}
+		members = append(members, m)
+	}
+
+	w.Header().Set("Content-Type", "application/json")
+	json.NewEncoder(w).Encode(members)
+}