feat: add admin endpoint to send digest emails for users

- Implemented a new endpoint `/admin/test/send-digest` in `admin_api.py` to trigger digest emails for specific users.
- Added a script `send_digest.py` to facilitate sending digest emails via the admin API.
- Enhanced the digest action handling in `digest_action_api.py` to support token peeking without consuming it.
- Updated the `send_digests` function in `digest_scheduler.py` to utilize the new `send_digest_for_user` function for sending emails.
- Introduced a new utility function `peek_token` in `digest_token.py` to validate tokens without consuming them.
- Modified the `ParentView.vue` component to handle digest actions upon receiving a digest token in the URL.
- Updated `.gitignore` to exclude sensitive certificate files.

frontend/vue-app/src/components/child/ParentView.vue

@@ -651,6 +651,24 @@ onMounted(async () => {
       const idParam = Array.isArray(route.params.id) ? route.params.id[0] : route.params.id
       const scrollToId = typeof route.query.scrollTo === 'string' ? route.query.scrollTo : null
       const entityType = typeof route.query.entityType === 'string' ? route.query.entityType : null
+      const digestToken =
+        typeof route.query.digestToken === 'string' ? route.query.digestToken : null
+
+      if (digestToken) {
+        try {
+          const res = await fetch(`/api/digest-action/${digestToken}`, {
+            method: 'POST',
+            credentials: 'include',
+          })
+          if (!res.ok) {
+            const data = await res.json().catch(() => ({}))
+            console.warn('Digest action failed:', data.error || res.status)
+          }
+        } catch (e) {
+          console.warn('Digest action request failed:', e)
+        }
+      }
+
       if (idParam !== undefined) {
         const promise = fetchChildData(idParam)
         promise.then((data) => {