install.md: add MySQL 8 auth compatibility note (flUseMySql2)

Lee la sección Create your database en install.md e inspecciona package.json para confirmar las dependencias mysql y mysql2 mencionadas en el issue. Añade la nota de compatibilidad con MySQL 8 después del bloque del esquema, incluida la configuración flUseMySql2 y la aclaración de que no se necesita ninguna instalación adicional; se considera completado cuando las instrucciones de configuración son claras para los usuarios de MySQL 8.

Problem

MySQL 8.0+ changed the default authentication plugin to caching_sha2_password. The older mysql npm package (used by davesql when flUseMySql2 is absent or false) only speaks mysql_native_password, so the server logs this error at startup and cannot reach the database:

ER_NOT_SUPPORTED_AUTH_MODE: Client does not support authentication protocol requested by server; consider upgrading MySQL client

This affects anyone running the current mysql:8 Docker image (which is 8.4.x), or any self-managed MySQL 8.0+ instance with default settings. MySQL 8.4 additionally removed mysql_native_password entirely, so there is no workaround on the MySQL side without recompiling or enabling a deprecated plugin.

Fix

davesql already supports mysql2, which handles caching_sha2_password natively. Setting one flag in config.json switches to it — no extra npm install needed, both packages ship with package.json:

"database": {
    "host": "127.0.0.1",
    "port": 3306,
    "user": "rsschat",
    "password": "...",
    "charset": "utf8mb4",
    "connectionLimit": 100,
    "database": "rsschat",
    "flUseMySql2": true
    }

Suggested doc addition

A short note in the Create your database section of install.md, after the schema block:

MySQL 8 compatibility: MySQL 8.0+ uses caching_sha2_password by default, which the mysql npm package does not support. Add "flUseMySql2": true to the database block in config.json. Both mysql and mysql2 are already in package.json — no extra install needed.

Alternatively, davesql could default flUseMySql2 to true since mysql2 is a strict superset and MySQL 8 is now the norm.

Surfaced during a fresh install against mysql:8 (8.4.10) on Ubuntu, following the current install.md instructions.
Issue formulated by Claude Code