feat(09-02): add certManager i18n namespace (de + en)

- Added certManager namespace to de.json with full key set (tabs, dropZone, paste, password, or, actions, emptyState, error)
- Added certManager namespace to en.json with matching key structure
- German copy matches UI-SPEC Copywriting Contract exactly
- Both files share identical key paths under certManager

apps/web/src/messages/en.json

@@ -391,5 +391,49 @@
     "detailVersion": "Version {version}",
     "detailStatusActive": "Activated for this tenant",
     "detailStatusInactive": "Not activated"
+  },
+  "certManager": {
+    "title": "Certificate Manager",
+    "description": "Inspect, split, merge and convert certificates.",
+    "tabs": {
+      "inspect": "Inspect",
+      "split": "Split",
+      "merge": "Merge",
+      "convert": "Convert"
+    },
+    "dropZone": {
+      "placeholder": "Drag file here or click to browse",
+      "formats": ".pem, .crt, .cer, .der, .pfx, .p12, .p7b, .p7c"
+    },
+    "paste": {
+      "placeholder": "Paste PEM content (-----BEGIN ...)"
+    },
+    "password": {
+      "label": "Password (PFX/P12)"
+    },
+    "or": "or",
+    "actions": {
+      "inspect": "Inspect",
+      "split": "Split",
+      "merge": "Merge",
+      "convert": "Convert",
+      "download": "Download",
+      "processing": "Processing..."
+    },
+    "emptyState": {
+      "inspect": "No certificate loaded.",
+      "inspectBody": "Upload a file or paste PEM text.",
+      "split": "No file loaded.",
+      "splitBody": "Upload a fullchain or P7B file.",
+      "merge": "No certificates selected.",
+      "mergeBody": "Upload at least two files.",
+      "convert": "No file loaded.",
+      "convertBody": "Upload a file and select an output format."
+    },
+    "error": {
+      "generic": "Processing failed. Check the file format or password.",
+      "wrongPassword": "Wrong password. Could not decrypt the PFX/P12 file.",
+      "unknownFormat": "Unknown format. The file could not be recognized as a certificate."
+    }
   }
 }