🔥(backend) remove all code related to template

The template feature is removed.
Migration created to drop related tables.
Files modified:
- viewsets
- serializers
- models
- admin
- factories
- urls
- tests
- demo data

CHANGELOG.md

@@ -10,6 +10,12 @@ and this project adheres to
 
 - ✨(frontend) integrate configurable Waffle #1795
 
+### Changed
+
+- ♿(frontend) improve accessibility:
+  - ♿️(frontend) fix subdoc opening and emoji pick focus #1745
+- ✨(backend) add field for button label in email template #1817
+
 ### Fixed
 
 - ✅(e2e) fix e2e test for other browsers #1799
@@ -17,17 +23,14 @@ and this project adheres to
 - 🐛(frontend) fix emojipicker closing in tree #1808
 - 🐛(frontend) display children in favorite #1782
 
-### Changed
+### Removed
 
-- ♿(frontend) improve accessibility:
-  - ♿️(frontend) fix subdoc opening and emoji pick focus #1745
-- ✨(backend) add field for button label in email template #1817
+- 🔥(project) remove all code related to template #1780
 
 ### Security
 
 - 🔒️(trivy) fix vulnerability about jaraco.context #1806
 
-
 ## [4.4.0] - 2026-01-13
 
 ### Added