Audit-log bug report status changes (B-60)

Every other admin mutation — config edit, pause/resume, privkey export, password
reset — leaves a trace; this one could silently mark a report resolved. With one
shared ADMIN_TOKEN and no per-admin identity, the audit log is the only
accountability there is.

bug_report_status_changed records the report id and the before/after status, and
carries the report's author as user_id so the entry is traceable from either
side. Nothing is written when the status doesn't actually change, matching
config_updated: an edit that changes nothing isn't an event, and noise hides the
real changes.

Also documents the new event in docs/guida-admin.md's audit table.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/api/routes/admin.py

@@ -408,7 +408,20 @@ async def update_bug_report_status(
     if report is None:
         raise HTTPException(status.HTTP_404_NOT_FOUND, "bug report not found")
 
-    report.status = body.status
+    # B-60: every other admin mutation (config edit, pause/resume, privkey export,
+    # password reset) leaves a trace; this one silently marked a report `resolved`.
+    # With one shared ADMIN_TOKEN and no per-admin identity, the audit log is the
+    # only accountability there is. Before/after like config_updated, and nothing
+    # written when the status doesn't actually change — re-clicking the status a
+    # report already has isn't an event.
+    if report.status != body.status:
+        await write_audit_log(
+            session,
+            "bug_report_status_changed",
+            {"report_id": report_id, "from": report.status, "to": body.status},
+            user_id=report.user_id,
+        )
+        report.status = body.status
     await session.commit()
 
     username = None