feat(master-data): make E-Taxes Item Group and Classification code read-only

These doctypes are now populated exclusively from master_data JSON via the
hash-diff sync, so block create/write/delete in the UI and API by dropping
those permissions. The sync itself writes at the DB level (db_insert /
set_value / delete_doc with ignore_permissions) so it is unaffected. Also
marks classification_name read_only and drops allow_import/allow_rename.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

invoice_az/invoice_az/doctype/classification_code/classification_code.json

@@ -1,7 +1,5 @@
 {
  "actions": [],
- "allow_import": 1,
- "allow_rename": 1,
  "autoname": "prompt",
  "creation": "2026-01-14 18:24:22.480170",
  "doctype": "DocType",
@@ -13,7 +11,8 @@
   {
    "fieldname": "classification_name",
    "fieldtype": "Text",
-   "label": "Classification Name"
+   "label": "Classification Name",
+   "read_only": 1
   }
  ],
  "grid_page_length": 50,
@@ -27,16 +26,13 @@
  "owner": "Administrator",
  "permissions": [
   {
-   "create": 1,
-   "delete": 1,
    "email": 1,
    "export": 1,
    "print": 1,
    "read": 1,
    "report": 1,
    "role": "System Manager",
-   "share": 1,
-   "write": 1
+   "share": 1
   }
  ],
  "row_format": "Dynamic",

invoice_az/invoice_az/doctype/e_taxes_item_group/e_taxes_item_group.json

@@ -52,8 +52,7 @@
    "read": 1,
    "report": 1,
    "role": "System Manager",
-   "share": 1,
-   "write": 1
+   "share": 1
   },
   {
    "email": 1,