(release) Add Django changelog page

Expose the repository CHANGELOG.md through a staff-only Django view and
link it from the main navigation.

Render a small safe subset of Markdown without adding a runtime dependency,
copy the changelog into the Docker image, and cover the page with view tests.

src/pobsync_backend/views.py

@@ -15,6 +15,7 @@ from django.shortcuts import get_object_or_404, redirect, render
 from django.utils import timezone
 from django.views.decorators.http import require_POST
 
+from pobsync import __version__
 from pobsync.errors import PobsyncError
 from pobsync.config.defaults import DEFAULT_EXCLUDES, DEFAULT_RSYNC_ARGS
 
@@ -88,6 +89,28 @@ def dashboard(request):
     return render(request, "pobsync_backend/dashboard.html", context)
 
 
+@staff_member_required
+def changelog(request):
+    changelog_path = Path(settings.BASE_DIR) / "CHANGELOG.md"
+    try:
+        changelog_text = changelog_path.read_text(encoding="utf-8")
+        missing = False
+    except FileNotFoundError:
+        changelog_text = "CHANGELOG.md was not found in this installation."
+        missing = True
+
+    return render(
+        request,
+        "pobsync_backend/changelog.html",
+        {
+            "app_version": __version__,
+            "changelog_blocks": _parse_changelog(changelog_text),
+            "changelog_path": changelog_path,
+            "missing": missing,
+        },
+    )
+
+
 @staff_member_required
 def self_check(request):
     checks = collect_self_checks()
@@ -793,6 +816,49 @@ def _pretty_json(value: object) -> str:
     return json.dumps(value or {}, indent=2, sort_keys=True)
 
 
+def _parse_changelog(text: str) -> list[dict[str, object]]:
+    blocks: list[dict[str, object]] = []
+    paragraph: list[str] = []
+    list_items: list[str] = []
+
+    def flush_paragraph() -> None:
+        if paragraph:
+            blocks.append({"kind": "paragraph", "text": " ".join(paragraph)})
+            paragraph.clear()
+
+    def flush_list() -> None:
+        if list_items:
+            blocks.append({"kind": "list", "items": list(list_items)})
+            list_items.clear()
+
+    for raw_line in text.splitlines():
+        line = raw_line.strip()
+        if not line:
+            flush_paragraph()
+            flush_list()
+            continue
+
+        if line.startswith("#"):
+            flush_paragraph()
+            flush_list()
+            marker, _space, heading = line.partition(" ")
+            level = min(max(len(marker), 1), 3)
+            blocks.append({"kind": "heading", "level": level, "text": heading.strip() or line.lstrip("#").strip()})
+            continue
+
+        if line.startswith("- "):
+            flush_paragraph()
+            list_items.append(line[2:].strip())
+            continue
+
+        flush_list()
+        paragraph.append(line)
+
+    flush_paragraph()
+    flush_list()
+    return blocks
+
+
 def _snapshot_restore_guidance(snapshot: SnapshotRecord) -> dict[str, str]:
     source_path = Path(snapshot.path) / "data"
     destination_path = Path("/restore") / snapshot.host.host