Replace from-scratch rewrite with real ngoduykhanh/wireguard-ui fork

The from-scratch Go rewrite had unresolved bugs (missing go.sum, UI
404s, path issues) from being built without a working local Go
toolchain to verify against. Switching strategy: use the actual
upstream wireguard-ui codebase (proven, battle-tested single-server
manager) as the base, and extend it for multi-server support instead
of re-deriving everything from zero.

Kept our own installers (bootstrap.sh, update.sh, scripts/install.sh,
scripts/proxmox-install.sh) - these still apply, just need updating
to build/install the upstream module layout instead of the old
cmd/wireguard-ui-multi structure.

Module path intentionally left as upstream's own
(github.com/ngoduykhanh/wireguard-ui) for now to avoid touching every
internal import; revisit if this needs to be fully rebranded.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

store/store.go

@@ -0,0 +1,30 @@
+package store
+
+import (
+	"github.com/ngoduykhanh/wireguard-ui/model"
+)
+
+type IStore interface {
+	Init() error
+	GetUsers() ([]model.User, error)
+	GetUserByName(username string) (model.User, error)
+	SaveUser(user model.User) error
+	DeleteUser(username string) error
+	GetGlobalSettings() (model.GlobalSetting, error)
+	GetServer() (model.Server, error)
+	GetClients(hasQRCode bool) ([]model.ClientData, error)
+	GetClientByID(clientID string, qrCode model.QRCodeSettings) (model.ClientData, error)
+	SaveClient(client model.Client) error
+	DeleteClient(clientID string) error
+	SaveServerInterface(serverInterface model.ServerInterface) error
+	SaveServerKeyPair(serverKeyPair model.ServerKeypair) error
+	SaveGlobalSettings(globalSettings model.GlobalSetting) error
+	GetWakeOnLanHosts() ([]model.WakeOnLanHost, error)
+	GetWakeOnLanHost(macAddress string) (*model.WakeOnLanHost, error)
+	DeleteWakeOnHostLanHost(macAddress string) error
+	SaveWakeOnLanHost(host model.WakeOnLanHost) error
+	DeleteWakeOnHost(host model.WakeOnLanHost) error
+	GetPath() string
+	SaveHashes(hashes model.ClientServerHashes) error
+	GetHashes() (model.ClientServerHashes, error)
+}