[client] recovery: add force keybind

Add a configured escape key plus Shift+R command that requests display
recovery from the LGMP transport and switches video to SPICE.

Track the request on the main thread, report its asynchronous result,
and return its producer instance with the request serial for exact
correlation.

Preserve normal escape+R rotation behavior, including custom Shift
escape keys.

client/src/main.h

@@ -116,6 +116,7 @@ struct AppState
 
   atomic_bool fallbackEndpointMismatch;
   atomic_uint transportLost;
+  atomic_bool forceRecovery;
 
   uint8_t guestUUID[16];
   bool    guestUUIDValid;
@@ -130,6 +131,8 @@ struct AppState
   uint64_t             escapeTime;
   int                  escapeAction;
   bool                 escapeKeys[KEY_MAX];
+  bool                 escapeShiftKeys[KEY_MAX];
+  atomic_uint          keyModifiers;
   bool                 escapeHelp;
   struct ll          * bindings;
   bool                 haveSrcSize;
@@ -265,8 +268,11 @@ struct KeybindHandle
 {
   int          sc;
   KeybindFn    callback;
+  KeybindFn    shiftCallback;
   const char * description;
+  const char * shiftDescription;
   void *       opaque;
+  void *       shiftOpaque;
 };
 
 enum WarpState