fix(migration): make kyte_locked migration portable to MySQL (v4.15.1, KYTE-#325)

[kennethphough]

What

Rewrites migrations/4.15.0_datamodel_kyte_locked.sql to be engine-portable (MySQL + MariaDB), replacing the MariaDB-only ADD COLUMN IF NOT EXISTS with an information_schema guard + prepared statement. Ships as v4.15.1.

Why

The migration (added in #111) used ALTER TABLE ... ADD COLUMN IF NOT EXISTS, which is MariaDB-only — it's a syntax error on MySQL 5.7/8.0. This surfaced during the v4.15.0 rollout to the first MySQL-backed install (ETOM, MySQL 8.0.44).

• No install was harmed: ETOM's kyte_locked columns already existed, so the failed statement was a no-op, and the decimal migration (portable) succeeded. The MariaDB clients applied the original fine.
• But it was latently broken: a drifted MySQL install would have errored and never gained the column, leaving the v4.15.0 model-level lock guard inert — the opposite of the migration's purpose.

Fix

Idempotent, portable pattern:

SET @col_exists := (SELECT COUNT(*) FROM information_schema.COLUMNS
    WHERE TABLE_SCHEMA=DATABASE() AND TABLE_NAME='DataModel' AND COLUMN_NAME='kyte_locked');
SET @ddl := IF(@col_exists=0, 'ALTER TABLE `DataModel` ADD COLUMN `kyte_locked` INT UNSIGNED NULL DEFAULT 0', 'DO 0');
PREPARE stmt FROM @ddl; EXECUTE stmt; DEALLOCATE PREPARE stmt;

(repeated for ModelAttribute).

Validation

Ran the new pattern live against both engines — clean, exit 0, columns intact:

• MySQL 8.0.44 (ETOM shipyard) — the engine that rejected the old syntax
• MariaDB 11.8.6 (dev)

Impact

Migration-only; no PHP change. Installs already on v4.15.0 with the columns present need no action — the deployed clients do not require re-rolling. Protects future/fresh/drifted MySQL installs.

🤖 Generated with Claude Code