feat(notifications): add leave, kick and ban notifications with actor pills

Extend the notification system to include member leave, kick and ban events,
mirroring the existing join notification functionality.

### Changes
- Added `_handle_leave_notifications` to process LEAVE, KICK and BAN events
- Integrated new notifications into existing membership event handlers
- Introduced `{actor}` placeholder with Matrix URI pill support
- Added `{actor_display}` as plaintext fallback
- Extended template renderer to support actor context
- Ensured consistent rendering across plaintext and HTML messages
- Added template cleanup for cases without an actor (e.g. voluntary leave)

### Templates
New placeholders:
- `{actor}` → clickable Matrix user pill
- `{actor_display}` → plain display name

### Configuration
New config keys:
- `leave_notification_message`
- `kick_notification_message`
- `ban_notification_message`

### Notes
- Fully async and non-blocking implementation
- Backwards compatible with existing templates
- No impact on join notification logic
- Scoped to rooms within configured space

maubot.yaml

@@ -2,7 +2,7 @@ maubot: 0.1.0
 id: advanced-community-bot
 name: Advanced Community Bot
 description: Advanced Community Bot is a Maubot Bot Plugin to manage Matrix servers. 
-version: 1.0.0
+version: 1.0.1
 license: MIT
 
 modules: