feat: add create materialized view table menu action

[emrberk]

Generate a starter CREATE MATERIALIZED VIEW from a table or an existing materialized view, and insert it into the editor for the user to tweak.

From a table:

• Menu item disabled for non-WAL tables and tables without a designated timestamp
• View name <table>_<sample>, replacing existing period suffix (e.g. my_table_5m → my_table_1h)
• REFRESH IMMEDIATE; SAMPLE BY / PARTITION BY / TTL inferred per QuestDB's default inference
• Column aggregates: sum/last by name pattern; types without a last() overload (BINARY, LONG128, INTERVAL, arrays) dropped

From a materialized view (downsample):

• SAMPLE BY stepped one ladder rung up; WITH BASE re-rooted at the source mat view
• Aggregate args rewritten to layer-1 aliases; count() → sum; count(DISTINCT …) dropped; non-decomposable aggregates fall back to last()
• WHERE / GROUP BY / LATEST ON stripped (source mat view already applied them)
• REFRESH, PERIOD, OWNED BY preserved; TTL stepped one rung up

Generation errors surface through the toast instead of being swallowed.