fix: prevent crash when opening Oracle views with LONG columns

[datlechin]

Summary

• OracleNIO (v1.0.0-rc.4) crashes with EXC_BREAKPOINT in OracleBackendMessageDecoder.decode when decoding LONG/LONG RAW column data — this is an unrecoverable precondition failure
• Many Oracle system views contain LONG columns, so clicking any such view crashes the app
• Detect SELECT * queries in OraclePlugin.execute(), pre-fetch column metadata from ALL_TAB_COLUMNS, and rewrite to an explicit column list replacing LONG/LONG RAW with NULL AS "col"
• Cache unsafe column names per table so buildBrowseQuery/buildFilteredQuery also exclude them on subsequent pagination/sorting/filtering
• Thread-safe cache access via NSLock, uppercase-normalized column matching, fast-path skip for non-* queries

Closes #564

Test plan

• Connect to Oracle (e.g. gvenzl/oracle-free container)
• Click a system view that has LONG columns (e.g. ALL_VIEWS, ALL_TAB_COLUMNS) — should open without crash
• Click a regular table — should open normally (no performance regression)
• Paginate/sort/filter on a view with LONG columns — should work without crash
• Verify LONG columns show NULL values in the data grid