refactor: extract core server package with handlers, routes, and lifecycle

Created server package with:
- server.go: Server struct and core methods
- handlers.go: HTTP handlers for health, KV operations, cluster management
- routes.go: HTTP route setup
- lifecycle.go: Server startup/shutdown logic

This moves ~400 lines of server-related code from main.go to dedicated
server package for better organization.

🤖 Generated with [Claude Code](https://claude.ai/code)

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

server/routes.go

@@ -0,0 +1,54 @@
+package server
+
+import (
+	"github.com/gorilla/mux"
+)
+
+// setupRoutes configures all HTTP routes and their handlers
+func (s *Server) setupRoutes() *mux.Router {
+	router := mux.NewRouter()
+
+	// Health endpoint
+	router.HandleFunc("/health", s.healthHandler).Methods("GET")
+
+	// KV endpoints
+	router.HandleFunc("/kv/{path:.+}", s.getKVHandler).Methods("GET")
+	router.HandleFunc("/kv/{path:.+}", s.putKVHandler).Methods("PUT")
+	router.HandleFunc("/kv/{path:.+}", s.deleteKVHandler).Methods("DELETE")
+
+	// Member endpoints
+	router.HandleFunc("/members/", s.getMembersHandler).Methods("GET")
+	router.HandleFunc("/members/join", s.joinMemberHandler).Methods("POST")
+	router.HandleFunc("/members/leave", s.leaveMemberHandler).Methods("DELETE")
+	router.HandleFunc("/members/gossip", s.gossipHandler).Methods("POST")
+	router.HandleFunc("/members/pairs_by_time", s.pairsByTimeHandler).Methods("POST") // Still available for clients
+
+	// Merkle Tree endpoints
+	router.HandleFunc("/merkle_tree/root", s.getMerkleRootHandler).Methods("GET")
+	router.HandleFunc("/merkle_tree/diff", s.getMerkleDiffHandler).Methods("POST")
+	router.HandleFunc("/kv_range", s.getKVRangeHandler).Methods("POST") // New endpoint for fetching ranges
+
+	// User Management endpoints
+	router.HandleFunc("/api/users", s.createUserHandler).Methods("POST")
+	router.HandleFunc("/api/users/{uuid}", s.getUserHandler).Methods("GET")
+	router.HandleFunc("/api/users/{uuid}", s.updateUserHandler).Methods("PUT")
+	router.HandleFunc("/api/users/{uuid}", s.deleteUserHandler).Methods("DELETE")
+
+	// Group Management endpoints
+	router.HandleFunc("/api/groups", s.createGroupHandler).Methods("POST")
+	router.HandleFunc("/api/groups/{uuid}", s.getGroupHandler).Methods("GET")
+	router.HandleFunc("/api/groups/{uuid}", s.updateGroupHandler).Methods("PUT")
+	router.HandleFunc("/api/groups/{uuid}", s.deleteGroupHandler).Methods("DELETE")
+
+	// Token Management endpoints
+	router.HandleFunc("/api/tokens", s.createTokenHandler).Methods("POST")
+
+	// Revision History endpoints
+	router.HandleFunc("/api/data/{key}/history", s.getRevisionHistoryHandler).Methods("GET")
+	router.HandleFunc("/api/data/{key}/history/{revision}", s.getSpecificRevisionHandler).Methods("GET")
+
+	// Backup Status endpoint
+	router.HandleFunc("/api/backup/status", s.getBackupStatusHandler).Methods("GET")
+
+	return router
+}