Feature: Offline device history with delete and remote uninstall

Persist every device that has ever logged in to the Go server in a small
JSON store (devices.json, overridable with YAMA_DEVICES_FILE and capped by
YAMA_DEVICES_MAX, default 1000 newest). The store follows the users.json
convention: atomic temp-file write with fsync and rename, a 500 ms debounce
for bursts of reconnects, first_seen preserved across logins, and pruning
that evicts offline records before devices that are still connected.
Devices connected at shutdown are stamped offline before the final flush so
last_seen stays accurate across restarts.

The server advertises an offlineDevices capability and device_list now
appends historical devices that are not online, marked with online:false and
last_seen. The web UI shows an Offline checkbox after Total/Showing (state
kept in localStorage), renders offline cards dimmed and dashed, and always
lists them in the screen-wall sidebar. Older servers without the capability
keep the online-only list.

Grid and List cards gain a delete button after the terminal button, admin
only, behind a confirmation dialog. Deleting an offline device removes its
history record; deleting an online device first sends the single-byte
TOKEN_UNINSTALL command (matching the MFC OnOnlineUninstall flow) and then
removes the record too, so the device does not come back as a dead offline
entry. The agent's own disconnect then runs the existing cleanup path:
screen and terminal sub-connections are closed, the hub entry is removed,
and browsers receive device_offline to release their watch sets, wall
sessions, and stream references. Wall mode exposes no delete action.

Tests cover history persistence/pruning/recovery, offline ordering, the
device_list merge, and all three delete outcomes (offline removal, online
uninstall with a single 0x3F byte, and viewer rejection).

Co-Authored-By: deepseek-flash

server/go/web/ws.go

@@ -10,6 +10,7 @@ import (
 	"time"
 
 	"github.com/gorilla/websocket"
+	"github.com/yuanyuanxiang/SimpleRemoter/server/go/devicehistory"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/hub"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/logger"
 	"github.com/yuanyuanxiang/SimpleRemoter/server/go/wsauth"
@@ -96,7 +97,7 @@ func (c *wsClient) close() {
 // challengeCaps advertises optional protocol features. It is appended to every
 // challenge, including the rotation after a failed login, because the browser
 // overwrites its capability state on each challenge. Old frontends ignore it.
-const challengeCaps = `,"caps":{"multiWatch":true,"keyframeRequest":true}`
+const challengeCaps = `,"caps":{"multiWatch":true,"keyframeRequest":true,"offlineDevices":true}`
 
 // maxWatchPerClient bounds the number of devices one WebSocket may stream at
 // once. The wall tops out at 25 tiles; the slack covers a focus switch racing
@@ -116,6 +117,7 @@ func (c *wsClient) isWatching(deviceID string) bool {
 type wsHub struct {
 	auth    *wsauth.Authenticator
 	devices *hub.Hub
+	history *devicehistory.Store // nil → device_list stays online-only
 	log     *logger.Logger
 
 	mu      sync.RWMutex
@@ -138,10 +140,11 @@ type wsHub struct {
 	trustForwardedFor bool // honor X-Forwarded-For (only when behind a trusted proxy)
 }
 
-func newWSHub(auth *wsauth.Authenticator, devices *hub.Hub, log *logger.Logger) *wsHub {
+func newWSHub(auth *wsauth.Authenticator, devices *hub.Hub, history *devicehistory.Store, log *logger.Logger) *wsHub {
 	h := &wsHub{
 		auth:              auth,
 		devices:           devices,
+		history:           history,
 		log:               log,
 		clients:           make(map[*wsClient]struct{}),
 		screenCloseTimers: make(map[string]*time.Timer),