feat(ui): add full table CSV download on database stats card

Each table row in the stats card now has a download button that exports
the entire table as CSV with proper column headers, generated server-side.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

html/lang/fr.json

@@ -98,7 +98,8 @@
     "statsTable": "Table",
     "statsCount": "Entrées",
     "statsOldest": "Plus ancienne",
-    "statsNewest": "Plus récente"
+    "statsNewest": "Plus récente",
+    "statsDownload": "CSV"
   },
   "logs": {
     "title": "Le journal",