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/partials/anonymize.htm

@@ -269,11 +269,14 @@
               </div>
               <div class="form-group">
                 <label class="paper-field-label" for="expirationDate">Expiration date</label>
-                <input class="form-control" type="date" name="expirationDate" id="expirationDate" ng-model="options.expirationDate" max="{{maxExpirationDate}}" />
+                <input class="form-control" type="date" name="expirationDate" id="expirationDate" ng-model="options.expirationDate" ng-class="{'is-invalid': anonymize.expirationDate.$invalid}" min="{{minExpirationDate}}" max="{{maxExpirationDate}}" required />
+                <div class="invalid-feedback" ng-show="anonymize.expirationDate.$error.min">Pick a date in the future.</div>
+                <div class="invalid-feedback" ng-show="anonymize.expirationDate.$error.max">Pick a date on or before {{maxExpirationDate | date}}.</div>
+                <div class="invalid-feedback" ng-show="anonymize.expirationDate.$error.required || anonymize.expirationDate.$error.date">Enter a valid expiration date.</div>
               </div>
             </div>
-            <small class="form-text text-muted" ng-show="options.expirationMode=='remove'">After {{options.expirationDate | date}}, the content will be removed.</small>
-            <small class="form-text text-muted" ng-show="options.expirationMode=='redirect'">After {{options.expirationDate | date}}, visitors will be redirected to GitHub.</small>
+            <small class="form-text text-muted" ng-show="options.expirationMode=='remove' && options.expirationDate">After {{options.expirationDate | date}}, the content will be removed.</small>
+            <small class="form-text text-muted" ng-show="options.expirationMode=='redirect' && options.expirationDate">After {{options.expirationDate | date}}, visitors will be redirected to GitHub.</small>
           </section>
 
           <section class="paper-settings-section" ng-show="isUpdate && detectedType === 'repo'">

public/partials/dashboard.htm

@@ -236,6 +236,9 @@
               <a class="dropdown-item" href="#" ng-show="item.status == 'removed'" ng-click="refreshItem(item)">
                 <i class="fas fa-check-circle"></i> Enable
               </a>
+              <a class="dropdown-item" href="#" ng-show="item.status == 'expired'" ng-click="extendItem(item)">
+                <i class="fas fa-calendar-plus"></i> Extend 6 months
+              </a>
               <a class="dropdown-item" href="#" ng-show="(item.status == 'ready' || item.status == 'expired' || item.status == 'error') && item.role !== 'coauthor'" ng-click="removeItem(item)">
                 <i class="fas fa-trash-alt"></i> Remove
               </a>