fix(admin): purge ALL scope overrides of merge_css/js setting

Migration 266 set dev/{css,js}/merge_{css,js}_files = 0 at the DEFAULT
scope but prod kept emitting merged-bundle URLs (each cache flush
produced a fresh hash, all of them 404). Diagnostic on prod confirmed
the bundle URL stayed in the rendered HTML across migration apply +
cache flush + Coolify redeploy.

Root cause: Magento config inheritance is default → website → store.
A leftover website- or store-scoped row in core_config_data with value
'1' shadowed the default '0'. The admin header's View As feature loads
whichever store context the operator picked, so a single website
override was enough to keep merging on for every admin page render —
and the merged bundle URL never existed on disk because the entrypoint
wipes media/js/* on every container start.

Fix: DELETE every row at every scope for the two paths, then INSERT
the default '0'. After this runs there's exactly one row per path
(scope=default, value=0) and no override can outrank it.

Pair with a cache-flush API call after deploy
(/reindex/api/flush?token=...) to invalidate the cached HTML still
referencing the dead bundle URL.

Author: unknown

migrations/271-purge-merge-css-js-overrides.sql

@@ -0,0 +1,20 @@
+-- 271: Purge every scope-level override of dev/css/merge_css_files and
+--      dev/js/merge_js_files, then reassert the default to '0'.
+--
+-- Background: migration 266 disabled CSS/JS merging at the DEFAULT scope, but
+-- prod is STILL emitting merged-bundle URLs in admin HTML — confirmed by a
+-- diagnostic that showed the merged bundle hash regenerating on each cache
+-- flush. Root cause: Magento's config inheritance is default → website →
+-- store, so a leftover website- or store-scoped row in core_config_data with
+-- value '1' shadows the default '0'. The "View As" feature in the admin
+-- header makes admin pages load whichever store context the operator is
+-- viewing under, so a single website override is enough to keep the broken
+-- merged bundle URL baked into the HTML.
+--
+-- Fix: delete EVERY existing row at any scope, then INSERT the default '0'.
+-- After this runs there is exactly one row per path, scope=default, value=0,
+-- and no scope can override it because no overrides exist.
+DELETE FROM core_config_data WHERE path IN ('dev/css/merge_css_files', 'dev/js/merge_js_files');
+INSERT INTO core_config_data (scope, scope_id, path, value) VALUES
+    ('default', 0, 'dev/css/merge_css_files', '0'),
+    ('default', 0, 'dev/js/merge_js_files',  '0');