fix: dashboard menu clickability + expiration date UX (#753)

* fix: dashboard menu clickability + expiration date UX

Dashboard actions menu:
- Inactive (expired/removed) rows dimmed via their cells instead of the
  row, so `opacity` no longer creates a stacking context that trapped the
  actions dropdown beneath later rows and made its items unclickable.
- Add an "Extend 6 months" menu item for expired repos/PRs/gists.

Expiration form (anonymize):
- Fix the "After , the content will be removed." blank date: guard the
  helper text and add min/max validation feedback so an invalid pick no
  longer nulls the model into a broken sentence.
- Add a `min` (today) so past dates can no longer be selected, and
  compute min/max from local date parts (not UTC) to avoid a timezone
  off-by-one in the native picker.
- Default expiration is now 6 months (single source of truth, removing a
  latent double-offset bug); max stays at 1 year.
- Block submitting a missing/out-of-range expiration date.

Backend:
- New POST /:id/extend endpoint for repos, PRs and gists that pushes the
  expiration +6 months and re-anonymizes so expired items come back
  online, mirroring the refresh flow. Shared extendExpirationDate helper.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

* fix: add frontend translation for invalid_status error code

The new /extend endpoints throw an "invalid_status" AnonymousError, which
the error-code coverage test requires to have a locale entry.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

---------

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

public/css/style.css

@@ -4289,7 +4289,12 @@ textarea::selection {
 .paper-table .paper-table-row:hover {
   background: var(--hover-bg-color);
 }
-.paper-table .paper-table-row.repo-inactive { opacity: 0.55; }
+/* Dim inactive rows through their cells rather than the row itself. Applying
+   opacity to the row creates a stacking context that traps the actions
+   dropdown menu (z-index) beneath the rows rendered after it, making its
+   items unclickable. Leave the actions column at full opacity so it stays
+   interactive. */
+.paper-table .paper-table-row.repo-inactive > *:not(.cell-actions) { opacity: 0.55; }
 .paper-table .paper-table-row.repo-error {
   background: rgba(180, 35, 24, 0.04);
   border-left: 2px solid #B42318;