v2.15.1

> [!NOTE]
> This release fixes Compose path and image handling, improves backup and update reliability, and adds a setting for Signal notifications.
> It also includes fixes for remote environments, authentication, and environment navigation.

### Compose and updates
- Interpolate variables in Compose include paths (#4298) — @kmendell
- Preserve Compose image spelling during project updates and self-updates (#4330) — @kmendell
- Keep the selected tag during self-updates and refresh stale project update status (commit `e862615fc4e47c8bf7fbfc089254bf509d0a82c7`) — @kmendell

### Environments, notifications, and authentication
- Resolve webhook target names in remote environments (#4299) — @kmendell
- Default `notifySelf` to `true` and add a setting for Signal notifications (#4302) — @Shraymonks
- Prevent logout from hanging on permission errors after OIDC login (#4309) — @kmendell
- Navigate to the selected environment on environment-scoped routes (#4320) — @kmendell

### Backups and maintenance
- Prevent system backups from failing when project files are in use (#4311) — @kmendell
- Allow deleting backups when their S3 repository no longer exists (#4319) — @kmendell
- Report accurate reclaimed space in scheduled pruning (#4317) — @kmendell
- Store Francis actor state in its own SQLite database (commit `93a740597df7a6aa47d5925d9d8dc5499934af05`) — @kmendell
- Use persistent Git storage for SSH host keys on native installs (#4300) — @kmendell

### Interface and platform
- Remove table header blur (commit `4d9bca092d6006b7265a6ce07928860b47ab84a5`) — @kmendell
- Release `arcane-cli` only for Apple Silicon (arm64), dropping amd64 support (commit `b3acb52dd02f39e39489203ce04ab316b47de8f6`) — @kmendell

### Internal changes
- Move the Docker utils package to `go.getarcane.app/docker` (#4296) — @kmendell
- Inline logic in project services (commit `73b43dba1e83f9a630b81e21381b533e50cdc57d`) — @kmendell