feat(sessions): add detail page, Notification component, and session API improvements

- add SessionDetailPage with breadcrumbs, DescriptionList, status badge, masked token
- add Notification component (info/success/error/warning/note variants) for contextual messages
- use Notification for 404 errors on session and environment detail pages
- add GET /sessions/:id endpoint; sanitize token (head…tail) and strip cookies/localStorage
- change DELETE /sessions/:id to return 204 No Content so client redirect works correctly
- add onRowClick prop to Table for clickable rows; stop propagation on actions column
- update status badges: open=success (green), closed=error (red) on both list and detail

client/src/i18n/locales/en.json

@@ -1,4 +1,10 @@
 {
+  "errors": {
+    "not_found": "Not found",
+    "not_found_session": "Session {{id}} does not exist or has been deleted.",
+    "not_found_environment": "Environment {{id}} does not exist or has been deleted.",
+    "generic": "Something went wrong. Please try again."
+  },
   "nav": {
     "environments": "Environments",
     "keys": "Keys",
@@ -48,7 +54,15 @@
     "col_status": "Status",
     "col_lastUsed": "Last Used",
     "empty": "No sessions yet.",
-    "action_delete": "Delete"
+    "loading": "Loading…",
+    "action_delete": "Delete",
+    "field_id": "ID",
+    "field_name": "Name",
+    "field_token": "Token",
+    "field_status": "Status",
+    "field_created": "Created",
+    "field_updated": "Updated",
+    "field_lastUsed": "Last Used"
   },
   "scenarios": {
     "title": "Scenarios",