refactor(setup): unify generated DB password handling across MySQL and PostgreSQL

[joshtrichards]

Summary

This refactor moves generated database-password creation into AbstractDatabase and reuses it in both MySQL and PostgreSQL setup flows.

Previously:

• MySQL generated a 30-character password with mixed character classes
• PostgreSQL generated a 30-character alphanumeric password via Server::get(ISecureRandom::class)

With this change:

• password generation is centralized in one helper
• MySQL keeps the existing stronger generation strategy
• PostgreSQL now uses the same generation strategy
• the PostgreSQL setup no longer relies on Server::get()

Why:

• removes duplicated password-generation logic
• keeps setup behavior consistent across database backends
• avoids service-locator usage where dependency injection is already available

Notes:

• generated symbols are filtered to avoid characters that are problematic in SQL string contexts: ", \, ', and ```

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)
• Labels added where applicable (ex: bug/enhancement, 3. to review, feature component)
• Milestone added for target branch/version (ex: 32.x for stable32)

AI (if applicable)

• The content of this PR was partly or fully generated using AI