ui: hide control footer in fullscreen; toggle fullscreen with the F key

The grid/archive control bar is hidden while its frame is fullscreen, so the
video fills the screen cleanly. A global F-key handler toggles fullscreen of
the active frame (live-main or arch-content) — entered and exited with F, and
exited with Esc as well. Uses e.code (KeyF) so it works on non-Latin layouts
and ignores typing in inputs and Ctrl/Cmd/Alt combos.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

frontend/static/style.css

@@ -240,6 +240,9 @@ footer.grid-bar {
 .tile:fullscreen { border: none; background: #000; }
 .tile:fullscreen video, .tile:fullscreen video-stream { object-fit: contain; }
 #grid:fullscreen { width: 100vw; height: 100vh; background: var(--bg); padding: 0; }
+/* в полноэкранном режиме панель-футер скрыта (вход/выход — клавиша F, выход также Esc) */
+#live-main:fullscreen .grid-bar,
+#arch-content:fullscreen .grid-bar { display: none; }
 .hevc-hint {
   position: absolute; left: 0; right: 0; bottom: 0; z-index: 3;
   background: rgba(63, 3, 3, .88); color: #fff; font-size: 11px;