feat(i18n): English source-string overrides + clear translation cache

Add locale/translations_en/{frappe,erpnext}/en.po so we can rewrite English
source strings we are not happy with. English is not special-cased anywhere in
Frappe's runtime, so setup_locale() picks these up with no changes: it derives
the locale from the translations_<lang> folder name, copies each en.po into the
target app and compiles it to sites/assets/locale/en/LC_MESSAGES/<app>.mo.
Both files ship empty (header only) for now.

Also clear the merged-translation cache once all .mo files are written.
bench migrate clears that cache *before* running after_migrate hooks, and it
refills during migration (patches and syncs call _() under lang "en"), so the
.mo files we write afterwards stayed invisible until someone ran
`bench clear-cache` by hand. This affected az/ru too.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

az_locale/locale/setup_locale.py

@@ -59,12 +59,31 @@ def setup_locale():
             # would otherwise keep serving a stale .mo.
             _compile_mo(app_name, lang)
 
+    _clear_translation_cache()
+
     print(
         f"[az_locale] Locale setup complete: {copied} file(s) copied, "
         f"{merged} extras merged, {skipped} skipped"
     )
 
 
+def _clear_translation_cache():
+    """Drop the cached merged-translation dict so the fresh .mo files are picked up.
+
+    `bench migrate` clears this cache *before* running after_migrate hooks, and the
+    cache refills during migration (patches and syncs call _() under lang "en").
+    Since we write the .mo files afterwards, they would stay invisible until someone
+    ran `bench clear-cache` by hand.
+    """
+    try:
+        import frappe.translate
+
+        frappe.translate.clear_cache()
+        print("[az_locale] Cleared translation cache")
+    except Exception as e:
+        print(f"[az_locale] Warning: could not clear translation cache ({e})")
+
+
 def _compile_mo(app_name, lang):
     """Compile the app's <lang>.po into the runtime .mo under sites/assets/locale/.
 

az_locale/locale/translations_en/erpnext/en.po

@@ -0,0 +1,26 @@
+#
+# English overrides for the "erpnext" app.
+#
+# This file is NOT a translation — it rewrites English source strings we are not
+# happy with. It is copied to apps/erpnext/erpnext/locale/en.po by setup_locale()
+# and compiled into sites/assets/locale/en/LC_MESSAGES/erpnext.mo on migrate.
+#
+# Rules:
+#   - msgid must match the source string byte for byte (case, punctuation,
+#     %s placeholders). Look them up in apps/erpnext/erpnext/locale/main.pot.
+#   - An empty msgstr means "no override" — the original string is used.
+#   - An override applies to that string everywhere. To narrow it down, add a
+#     msgctxt line above the msgid.
+#   - Keep this file small: the whole English dict ships in every session's boot.
+#
+# Example:
+#   msgid "Customer"
+#   msgstr "Client"
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: erpnext\n"
+"Language: en\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=utf-8\n"
+"Content-Transfer-Encoding: 8bit\n"

az_locale/locale/translations_en/frappe/en.po

@@ -0,0 +1,26 @@
+#
+# English overrides for the "frappe" app.
+#
+# This file is NOT a translation — it rewrites English source strings we are not
+# happy with. It is copied to apps/frappe/frappe/locale/en.po by setup_locale()
+# and compiled into sites/assets/locale/en/LC_MESSAGES/frappe.mo on migrate.
+#
+# Rules:
+#   - msgid must match the source string byte for byte (case, punctuation,
+#     %s placeholders). Look them up in apps/frappe/frappe/locale/main.pot.
+#   - An empty msgstr means "no override" — the original string is used.
+#   - An override applies to that string everywhere. To narrow it down, add a
+#     msgctxt line above the msgid.
+#   - Keep this file small: the whole English dict ships in every session's boot.
+#
+# Example:
+#   msgid "Submit"
+#   msgstr "Post"
+#
+msgid ""
+msgstr ""
+"Project-Id-Version: frappe\n"
+"Language: en\n"
+"MIME-Version: 1.0\n"
+"Content-Type: text/plain; charset=utf-8\n"
+"Content-Transfer-Encoding: 8bit\n"