FLIPPIX OS v0.5.0-alpha — USB File Bridge

Hardware-tested alpha release for Flipper Zero. Adds the native file browser and text viewer, the bidirectional USB File Bridge, directory listing, upload/download, mkdir/delete, per-block CRC32 validation, reliable consecutive CDC sessions, and the v0.5 status-bar label. The included root filesystem already contains /bin/filebridge. Tested with a physical Flipper Zero using a byte-identical 6768-byte binary round trip.