Add in-app deprecation warnings for PostgreSQL

[zackkrida]

Problem

Mathesar currently does not notify users when their connected databases, or the internal Mathesar database, is running a PostgreSQL version that is reaching end-of-life support by Mathesar.

Without warning, users might continue using deprecated PostgreSQL versions. This can lead to confusion after upgrades, and difficulty for maintainers in diagnosing version-related issues.

Proposed Solution

Introduce in-app deprecation warnings that alert users when Mathesar detects a deprecated PostgreSQL version in any database.

Example text

⚠️ Deprecation Notice: Your our connected database(s) {names} are running PostgreSQL 13, which will no longer be supported. starting in Mathesar 0.8.0. Please upgrade to PostgreSQL 14 or higher to ensure continued compatibility and support.

Additional Context

• Mathesar 0.8.0 will drop support for PostgreSQL 13.
• We don't currently do any in-app checking of Postgres versions, I believe, so this could require work across the stack