v0.0.45: call ring tones + group calls

Direct call ringing:
- Incoming: oscillator ring tone (440/480Hz, on/off pattern)
- Outgoing: ringback tone (2s on, 4s off) while waiting for answer
- Browser Notification API for background incoming calls
- All tones stop on answer/reject/hangup
- Notification permission requested on first click

Group calls:
- /gcall — start a group call (notifies all group members)
- /gjoin — join an active group call
- /gleave-call — leave group call
- /gmute — toggle per-group call notification mute (localStorage)
- Participant tracking (joined/left messages with count)
- Group call signal via group message broadcast (JSON type: group_call)
- Call bar shows "Join Call" button when group call is active
- Audio via same WZP bridge (room = gc-<groupname>)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

warzone/Cargo.toml

@@ -9,7 +9,7 @@ members = [
 ]
 
 [workspace.package]
-version = "0.0.44"
+version = "0.0.45"
 edition = "2021"
 license = "MIT"
 rust-version = "1.75"