ui: add a 22px bottom footer (brand + version)

Footer is a third layout block; .layout height now subtracts --footer-h (22px)
so it never overlaps the full-height video grid. Injected via JS only on pages
with the main layout (skips login); shows CoRE.Vision brand + version.

VERSION 0.0.135.

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

frontend/static/style.css

@@ -14,6 +14,7 @@
   --warn:      #f59e0b;
   --err:       #ef4444;
   --header-h:  48px;
+  --footer-h:  22px;
   --sidebar-w: 240px;
 }
 
@@ -47,7 +48,16 @@ nav a.active { background: var(--accent); color: #fff; }
 .clock { font-variant-numeric: tabular-nums; color: var(--text); }
 
 /* ── Раскладка ── */
-.layout { display: flex; height: calc(100% - var(--header-h)); }
+.layout { display: flex; height: calc(100% - var(--header-h) - var(--footer-h)); }
+
+/* ── Футер ── */
+footer.app-footer {
+  height: var(--footer-h); display: flex; align-items: center; gap: 14px;
+  padding: 0 14px; background: var(--panel); border-top: 1px solid var(--border);
+  font-size: 11px; color: var(--text-dim);
+}
+footer.app-footer .brand { font-size: 12px; }
+footer.app-footer #footer-version { font-variant-numeric: tabular-nums; }
 aside {
   width: var(--sidebar-w); background: var(--panel); border-right: 1px solid var(--border);
   display: flex; flex-direction: column; overflow: hidden;