v1.1.0 — working volume/mute + recording

Stable checkpoint: master volume, mute (no video blur), record toggle, and
working audio and video recording.

Since v1.0.0

• Master volume via ffmpeg gain (/volume, 🔉/🔊) — affects the whole room, with correct position tracking across re-feeds.
• Mute = volume 0 (🔇 / /vmute) so muting a video no longer makes it blurry.
• Record button is a toggle (⏺ Rec / Stop) on the control panel.
• Video recording now works: clamps the seek into the file, re-encodes audio to AAC (for E-AC3 MKVs), and re-encodes HEVC/non-H.264 video to H.264 720p so Telegram renders it. Audio recordings unchanged.
• Friendlier /radio error when no voice chat is open and the assistant can't start one.

Note: recording an HEVC title re-encodes on the CPU and can briefly stutter the live stream on modest hardware — GPU (VAAPI) offload is the next step.