core: fix security and concurrency issues found in a backend audit (#2805)

* core: fix security and concurrency issues found in backend audit

Security:
- privesc: pipe the sudo password via stdin (sudo -S) instead of
  embedding it in the command string, so it no longer appears in argv
  (readable by any local user via /proc/<pid>/cmdline or ps)
- greeter: tokenize a session .desktop Exec= line into argv and execve
  directly instead of running it through /bin/sh -c, closing a command-
  injection path via user-writable ~/.local/share/wayland-sessions
- plugins: reject path-separator/.. in plugin id/name before joining
  into a filesystem path, closing an arbitrary-directory-delete in the
  uninstall/update fallback
- keybinds/hyprland: always quote unrecognized bind actions/keys when
  writing generated Lua; only re-emit genuine round-tripped custom Lua
  verbatim (tracked via an explicit flag), closing a Lua-injection path
- desktop/mimeapps: reject newline/bracket in mime/desktop-id fields so
  they can't inject fake sections into the shared mimeapps.list

Robustness / concurrency:
- server: recover panics in the request-dispatch path so one bad
  handler can't crash the daemon and drop every client
- go-wayland: recover panics in the shared dispatch choke point so a
  malformed compositor event can't crash CLI tools / the daemon
- server: per-connection D-Bus client ID instead of a shared constant,
  fixing cross-client signal delivery and subscription teardown
- network: guard the NetworkManager device maps with a mutex (a
  concurrent map read/write here is an unrecoverable fatal error)
- cups: close the event channel on Stop() so Unsubscribe() of the last
  subscriber no longer deadlocks; allocate the fresh channel in Start()
- freedesktop: reuse the shared session conn for the settings watcher
  and tear it down in Close(), fixing a per-Manager conn+goroutine leak
- clipboard: mutex-guard lazy dbusConn creation
- geolocation: use WithMatchMember for the GeoClue2 LocationUpdated
  signal (was WithMatchSender with an interface.member string, so the
  match never fired and live location updates never arrived)
- screenshot: set failed=true on buffer/pool creation errors so the
  dispatch loop doesn't wait forever for a ready/failed that never comes

* apply code review comments

---------

Co-authored-by: bbedward <bbedward@gmail.com>

quickshell/Services/DMSService.qml

@@ -246,13 +246,14 @@ Singleton {
 
     function sendSubscribeRequest() {
         const request = {
-            "method": "subscribe"
+            "method": "subscribe",
+            "params": {
+                "clientId": dbusClientId
+            }
         };
 
         if (activeSubscriptions.length > 0) {
-            request.params = {
-                "services": activeSubscriptions
-            };
+            request.params.services = activeSubscriptions;
             log.debug("Subscribing to services:", JSON.stringify(activeSubscriptions));
         } else {
             log.debug("Subscribing to all services");
@@ -672,6 +673,7 @@ Singleton {
 
     signal dbusSignalReceived(string subscriptionId, var data)
 
+    readonly property string dbusClientId: "dms-qml-" + Date.now() + "-" + Math.floor(Math.random() * 0xffffffff)
     property var dbusSubscriptions: ({})
 
     function dbusCall(bus, dest, path, iface, method, args, callback) {
@@ -735,7 +737,8 @@ Singleton {
             "sender": sender || "",
             "path": path || "",
             "interface": iface || "",
-            "member": member || ""
+            "member": member || "",
+            "clientId": dbusClientId
         }, response => {
             if (!response.error && response.result?.subscriptionId) {
                 dbusSubscriptions[response.result.subscriptionId] = true;