(refactor) make Docker backup root static in Django setup

Remove backup_root from the normal Django global config form and display
the fixed container path /backups instead.

Always persist /backups from the setup form so Docker deployments do not
mix host paths with container paths.

Update tests and docs to clarify that the host backup directory is chosen
through the Docker mount, while Django always uses /backups internally.

README.md

@@ -129,15 +129,15 @@ docker compose up --build web scheduler worker
 ```
 
 The container persists `/opt/pobsync` and the SQLite database in Docker volumes.
-Backup data is mounted at `/backups` inside the containers. By default this uses `./backups` on the host.
-Override it with `POBSYNC_BACKUP_ROOT`:
+Backup data is always available at `/backups` inside the containers. By default this uses `./backups` on the host.
+Override the host-side mount with `POBSYNC_BACKUP_ROOT`:
 
 ```
 POBSYNC_BACKUP_ROOT=/mnt/backups/pobsync docker compose up --build web scheduler worker
 ```
 
-In the Django global config, set the backup root to `/backups` when running in Docker. For local, non-Docker use,
-set it directly to the host path, for example `/mnt/backups/pobsync`.
+The Django setup UI keeps the backup root fixed at `/backups`; only the Docker mount decides which host directory
+that points to.
 
 ## Docker With MariaDB
 

src/pobsync_backend/forms.py

@@ -84,7 +84,6 @@ class GlobalConfigForm(forms.ModelForm):
         model = GlobalConfig
         fields = (
             "name",
-            "backup_root",
             "ssh_user",
             "ssh_port",
             "ssh_options",
@@ -103,13 +102,13 @@ class GlobalConfigForm(forms.ModelForm):
         )
         help_texts = {
             "name": "Usually 'default'. The backup engine currently reads the default config.",
-            "backup_root": "Directory that contains host backup folders.",
             "default_source_root": "Used by hosts without a custom source root.",
             "default_destination_subdir": "Optional subdirectory below each snapshot.",
         }
 
     def save(self, commit: bool = True):
         instance = super().save(commit=False)
+        instance.backup_root = settings.POBSYNC_BACKUP_ROOT
         instance.pobsync_home = settings.POBSYNC_HOME
         if commit:
             instance.save()

src/pobsync_backend/templates/pobsync_backend/base.html

@@ -78,6 +78,7 @@
     .status.failed { color: var(--failed); border-color: #e8b4b4; background: #fff0f0; }
     .status.running { color: var(--running); border-color: #e7cf8a; background: #fff8df; }
     .stack { display: grid; gap: 4px; }
+    .stack.spaced { margin-bottom: 14px; }
     .two-col { display: grid; gap: 18px; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); }
     .actions { display: flex; flex-wrap: wrap; gap: 10px; margin: 0 0 18px; }
     .actions.inline { margin: 12px 0 0; }

src/pobsync_backend/templates/pobsync_backend/global_form.html

@@ -11,6 +11,10 @@
 
   <section class="panel">
     <h2>{% if global_config %}Edit Global Config{% else %}Create Global Config{% endif %}</h2>
+    <div class="stack spaced">
+      <div><strong>Backup root:</strong> {{ backup_root }}</div>
+      <div class="muted">This is the fixed path inside the Docker containers. Change the host directory by changing the Docker mount.</div>
+    </div>
     <form method="post" class="form-grid">
       {% csrf_token %}
       {{ form.non_field_errors }}

src/pobsync_backend/tests/test_views.py

@@ -75,7 +75,6 @@ class ViewTests(TestCase):
             reverse("edit_global_config"),
             {
                 "name": "default",
-                "backup_root": "/backups",
                 "ssh_user": "backup",
                 "ssh_port": "2222",
                 "ssh_options": "StrictHostKeyChecking=no\nBatchMode=yes",
@@ -109,7 +108,7 @@ class ViewTests(TestCase):
         self.assertEqual(config.retention_daily, 7)
         self.assertEqual(config.retention_yearly, 1)
 
-    def test_global_config_form_renders_saved_backup_root_on_edit(self) -> None:
+    def test_global_config_form_renders_static_container_backup_root_on_edit(self) -> None:
         self.client.force_login(self.staff_user)
         GlobalConfig.objects.create(
             name="default",
@@ -120,10 +119,48 @@ class ViewTests(TestCase):
         response = self.client.get(reverse("edit_global_config"))
 
         self.assertEqual(response.status_code, 200)
-        self.assertContains(response, "/mnt/pobsync/backups")
+        self.assertContains(response, "Backup root:")
+        self.assertContains(response, "/backups")
+        self.assertNotContains(response, "/mnt/pobsync/backups")
         self.assertNotContains(response, "/opt/pobsync/backups")
         self.assertNotContains(response, "Pobsync home")
 
+    def test_global_config_form_resets_backup_root_to_static_container_path(self) -> None:
+        self.client.force_login(self.staff_user)
+        GlobalConfig.objects.create(
+            name="default",
+            backup_root="/mnt/pobsync/backups",
+            pobsync_home="/custom/legacy/home",
+        )
+
+        response = self.client.post(
+            reverse("edit_global_config"),
+            {
+                "name": "default",
+                "ssh_user": "root",
+                "ssh_port": "22",
+                "ssh_options": "",
+                "rsync_binary": "rsync",
+                "rsync_args": "",
+                "rsync_extra_args": "",
+                "rsync_timeout_seconds": "0",
+                "rsync_bwlimit_kbps": "0",
+                "default_source_root": "/",
+                "default_destination_subdir": "",
+                "excludes_default": "",
+                "retention_daily": "14",
+                "retention_weekly": "8",
+                "retention_monthly": "12",
+                "retention_yearly": "0",
+            },
+            follow=True,
+        )
+
+        self.assertRedirects(response, reverse("dashboard"))
+        config = GlobalConfig.objects.get(name="default")
+        self.assertEqual(config.backup_root, "/backups")
+        self.assertEqual(config.pobsync_home, "/opt/pobsync")
+
     def test_create_host_config_form_creates_host(self) -> None:
         self.client.force_login(self.staff_user)
 

src/pobsync_backend/views.py

@@ -4,6 +4,7 @@ import json
 
 from django.contrib import messages
 from django.contrib.admin.views.decorators import staff_member_required
+from django.conf import settings
 from django.db.models import Count
 from django.shortcuts import get_object_or_404, redirect, render
 from django.views.decorators.http import require_POST
@@ -60,6 +61,7 @@ def edit_global_config(request):
         {
             "global_config": global_config,
             "form": form,
+            "backup_root": settings.POBSYNC_BACKUP_ROOT,
         },
     )
 
@@ -264,7 +266,6 @@ def _default_schedule_initial() -> dict[str, object]:
 def _default_global_initial() -> dict[str, object]:
     return {
         "name": "default",
-        "backup_root": "/backups",
         "ssh_user": "root",
         "ssh_port": 22,
         "rsync_binary": "rsync",

src/pobsync_server/settings.py

@@ -89,3 +89,4 @@ STATIC_ROOT = os.getenv("POBSYNC_STATIC_ROOT", str(BASE_DIR / "var" / "static"))
 DEFAULT_AUTO_FIELD = "django.db.models.BigAutoField"
 
 POBSYNC_HOME = os.getenv("POBSYNC_HOME", "/opt/pobsync")
+POBSYNC_BACKUP_ROOT = "/backups"