Escape "vector" reserved keyword for MariaDB 11.6+ support

[scotteuser]

"vector" became a reserved keyword in MariaDB 11.6+ resulting in errors like this:

mysqli_sql_exception: You have an error in your SQL syntax; check the manual that corresponds to your MariaDB server version for the right syntax to use near '
                normalized_vector JSON,
                magnitude DOUBLE,
  ...' at line 3

See https://mariadb.com/docs/server/reference/sql-structure/sql-language-structure/reserved-words

This PR just surrounds all usage of vector with backticks.

[scotteuser]

Created related issue here: #13

[mxr576]

Using embedding_vector instead could be an alternative fix that eliminates reserved word usage.

[scotteuser]

That'd need a migration path though to convert existing databases, it's far simpler to just wrap in backticks like this imo

[mxr576]

Agreed about the impact, was not sure about the BC policy here, just wanted to raise the alternative that removed reserved word usage.