## Summary

- Add per-host rsync bandwidth limit overrides with inherit/unlimited semantics.
- Store the effective bwlimit in run metadata/results and show it in host/run detail views.
- Document recommended starting values for VPN and remote backups.

## Tests
- `.venv/bin/python manage.py makemigrations --check --dry-run`
- `.venv/bin/python manage.py test src.pobsync_backend.tests.test_django_config_source.DjangoConfigSourceTests.test_returns_effective_config_from_database src.pobsync_backend.tests.test_django_config_source.DjangoConfigSourceTests.test_host_can_disable_global_rsync_bandwidth_limit src.pobsync_backend.tests.test_configure_commands.ConfigureCommandsTests.test_configure_host_uses_global_retention_defaults src.pobsync_backend.tests.test_run_scheduled_config_source.RunScheduledConfigSourceTests.test_dry_run_applies_configured_bandwidth_limit src.pobsync_backend.tests.test_run_scheduled_config_source.RunScheduledConfigSourceTests.test_real_run_can_request_verbose_output_args --verbosity 2`
- `.venv/bin/python manage.py test src.pobsync_backend.tests.test_views.ViewTests.test_create_host_config_form_creates_host src.pobsync_backend.tests.test_views.ViewTests.test_host_detail_renders_effective_config_preview src.pobsync_backend.tests.test_views.ViewTests.test_run_detail_renders_result_payload src.pobsync_backend.tests.test_views.ViewTests.test_host_config_form_updates_host_config --verbosity 2`
- `.venv/bin/python manage.py check`

Closes #51

src/pobsync_backend/models.py

@@ -63,6 +63,7 @@ class HostConfig(TimestampedModel):
     excludes_add = models.JSONField(default=list, blank=True)
     excludes_replace = models.JSONField(null=True, blank=True)
     rsync_extra_args = models.JSONField(default=list, blank=True)
+    rsync_bwlimit_kbps = models.PositiveIntegerField(null=True, blank=True)
     retention_daily = models.PositiveIntegerField(default=14)
     retention_weekly = models.PositiveIntegerField(default=8)
     retention_monthly = models.PositiveIntegerField(default=12)