feat(course): auto-enrol button for paid course join requests (#769)

* feat(course): add auto-enrol flow for paid course join requests

- Extend teacher buy-request email with manual access steps and an
  Auto Enrol this Student button
- Link teachers to the course People page with grantAccess query param
- Add grant-access modal that sends the same org audience invite used
  by the Invite new students flow

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(i18n): translate grant access modal strings

Replace English placeholders copied into non-en locale files with
proper translations for each supported language.

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(email): shorten auto-enrol button label per review

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(email): use American spelling Enroll in auto-enroll CTA

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

* fix(i18n): localize Danish grant-access send invite label

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

---------

Co-authored-by: Rotimi Best <rotimi-best@users.noreply.github.com>

apps/dashboard/src/lib/utils/translations/de.json

@@ -1198,6 +1198,12 @@
           "no_matching_existing_students": "No organization students match your search.",
           "notify_existing_students": "Send course access email",
           "grant_access": "Grant Access",
+          "grant_access_modal": {
+            "title": "Schülerzugang gewähren",
+            "description": "Gewähren Sie {email} Zugang zu diesem Kurs. Wir senden eine Einladungs-E-Mail, damit die Person Ihrer Organisation beitreten und in diesem Kurs eingeschrieben werden kann.",
+            "cancel": "Abbrechen",
+            "send_invite": "Einladung senden"
+          },
           "invite_new_students_title": "Invite new students",
           "invite_new_students_description": "Invite new people into your organization and pre-assign them to this course. They will create an account, accept the invite, and get access.",
           "invite_new_students": "Invite Students",