## 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/forms.py

@@ -60,6 +60,7 @@ class HostConfigForm(forms.ModelForm):
             "excludes_add",
             "excludes_replace",
             "rsync_extra_args",
+            "rsync_bwlimit_kbps",
             "retention_daily",
             "retention_weekly",
             "retention_monthly",
@@ -70,6 +71,7 @@ class HostConfigForm(forms.ModelForm):
             "ssh_user": "Leave empty to use the global SSH user.",
             "ssh_port": "Leave empty to use the global SSH port.",
             "source_root": "Leave empty to use the global default source root.",
+            "rsync_bwlimit_kbps": "Leave empty to inherit the global limit. Use 0 for unlimited on this host.",
         }
 
 
@@ -112,6 +114,7 @@ class GlobalConfigForm(forms.ModelForm):
         help_texts = {
             "name": "Usually 'default'. The backup engine currently reads the default config.",
             "default_ssh_credential": "Optional. Used by hosts without their own SSH credential.",
+            "rsync_bwlimit_kbps": "Rsync bandwidth limit in KB/s. Use 0 for unlimited.",
             "default_source_root": "Used by hosts without a custom source root.",
             "default_destination_subdir": "Optional subdirectory below each snapshot.",
         }