fix: ffmpeg version detection and player letterboxing

ffmpeg only accepts -version (single dash); it exits 8 on --version and
writes to stderr, so the status panel reported it missing even when
installed. Version flags are now per-tool and both streams are read.

The player used max-h-full inside a grid, which a 1080x1920 Short
overflowed. Switched to absolute fill with object-contain so portrait
and landscape both letterbox correctly.

Also sized the window to 1180x780 centered, which fits a laptop display.

src/components/Player.tsx

@@ -29,9 +29,11 @@ export default function Player({ item, path, onClose, onDelete }: Props) {
         </button>
       </div>
 
-      <div className="flex-1 min-h-0 bg-black grid place-items-center">
+      {/* Absolute fill + object-contain, so portrait Shorts and landscape
+          videos are both letterboxed to the pane instead of overflowing it. */}
+      <div className="flex-1 min-h-0 bg-black relative">
         <video key={path} src={fileUrl(path)} controls autoPlay
-          className="max-h-full max-w-full" />
+          className="absolute inset-0 h-full w-full object-contain" />
       </div>
 
       <div className="px-5 py-4 max-h-56 overflow-y-auto border-t border-edge">