Dashboard AI improvements

[gugu]

Is your feature request related to a problem? Please describe.

Sometimes AI-generated query has syntax errors, also it can be non-optimal.

Describe the solution you'd like

1. Panel AI query needs to go through feedback loop (request query => run explain for given query => request corrections based on explain result or error message => return query to user)
2. Automatic table dashboard endpoint - it receives table name, asks AI which charts would be useful for this table => feeds responses to panel AI agents

Describe alternatives you've considered

Using brain for SQL queries - not cool anymore