Enable STRICT_TRANS_TABLES: audit and fix INSERT/UPDATE paths

[Neophytis]

Context

The beta stack runs MariaDB 12, which enables STRICT_TRANS_TABLES by default. The application was built against Lion's MariaDB which had no strict mode, so many write paths silently rely on non-strict behaviour. With strict mode on, the following break:

• Gallery image uploads
• Sending messages
• Forum post submission
• Any INSERT/UPDATE hitting a NOT NULL column without a default value, a string longer than its column definition, or an invalid date literal

Current decision: STRICT_TRANS_TABLES is explicitly excluded from sql_mode in the beta DB config to match Lion's historical behaviour and unblock the migration:

sql_mode = NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION

This is tracked in sysadmins-infra hosts/bewelcome_alpha/compose/bewelcome/mariadb-tuning.cnf.

What needs fixing before re-enabling strict mode

1. Missing defaults — find NOT NULL columns that have no DEFAULT and ensure the application always provides a value on INSERT.
2. Silent string truncation — find VARCHAR/TINYTEXT columns where the application may insert a value longer than the column definition.
3. Invalid datetime literals — 0000-00-00 dates in queries or inserts must be replaced with NULL or a valid date.
4. Implicit integer coercion — out-of-range values on TINYINT/SMALLINT columns that were silently clamped.

How to find them

Run the application manually on beta with strict mode temporarily re-enabled and collect the resulting SQL errors from the slow query log or application logs. Each error points to a specific query.

Definition of done

All functional tests pass with sql_mode = STRICT_TRANS_TABLES,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION. At that point the override in sysadmins-infra can be removed.