Track the DHF document templates for repository sync

Why: The user dropped RDM DHF document templates at .templates/ for
upcoming use and wants them synced through the repository instead of a
local ignore; the temporary .gitignore entry is reverted and .DS_Store
junk is excluded.

Evidence: 44 template files staged (18MB, .doc/.docx across DHF stages);
.DS_Store ignored; working tree clean after staging (owner-directed
disposition of these files per session instruction).

Impact: Data-only addition under .templates/; .gitignore gains
.DS_Store; no code paths touched.

Refs: User instruction 2026-10-13 (templates to be used later).

.gitignore

@@ -1,6 +1,7 @@
 /bin/
 node_modules/
 __pycache__/
+.DS_Store
 *.py[cod]
 /data/
 /data-test/