[grade=A] DC-065: Sweep 15 console.* calls to process.stderr.write

Replace all non-logger console.error/warn calls with process.stderr.write
using tagged prefixes ([AuditLogger], [CSRF], [DNS Registry], etc.) for
grep-ability. All in fallback/catch paths where structured logger may be
unavailable. Test updated to use jest.spyOn with try/finally for clean
mock restoration.

Codex grade: pass (22,402 tokens). All 1539 tests pass.

dashcaddy-api/routes/backups.js

@@ -775,7 +775,7 @@ async function getStorageInfo() {
         : 0;
     }
   } catch (error) {
-    console.error('[BackupsRouter] Error getting storage info:', error.message);
+    process.stderr.write(`[BackupsRouter] Error getting storage info: ${error.message}\n`);
   }
 
   return result;