feat: soft-split SQL statements at 2+ blank lines when ; is missing

[Blankll]

Changes

1. Soft-split SQL statements at blank lines (当 ; 忘记时自动分割)

Added splitRangesAtBlankLines() that runs after the standard ;-based split. When 2+ consecutive blank lines are followed by a SQL keyword, the range is split at that point.

Split keywords: SELECT, CREATE, ALTER, DROP, INSERT, UPDATE, DELETE, TRUNCATE, GRANT, REVOKE, EXPLAIN, SHOW, DESCRIBE, USE, SET, CALL, EXEC/EXECUTE, BEGIN, COMMIT, ROLLBACK, DECLARE, ANALYZE, VACUUM, PRAGMA, REFRESH, COPY, WITH, MERGE, REPLACE

Safety: Requires 2+ blank lines (not 1) — a single blank line within a multi-line statement won't split it.

CTE protection: When the segment starts with WITH, suppresses soft-split for the next DML keyword (SELECT/INSERT/UPDATE/DELETE) since it's the main query of a CTE, not a new statement.

2. Table view toolbar fixes

• Fixed refresh icon: i-carbon-refresh does not exist in Carbon icons → changed to i-carbon-renew (same icon as "Reload database list")
• Fixed nested button bug: Refresh button was wrapping the columns dropdown (<button> inside <button>) — properly separated
• Icons inside inputs: Search and filter icons moved from outside to inside the input boxes (absolute positioned), saving toolbar space
• Removed separator: Visual separator between search and filter removed (no longer needed)
• Consistent style: Refresh button uses variant="ghost" like other toolbar icon buttons

3. Export filename format

Default CSV export filename changed from {tableName}.csv to {connectionName}-{databaseName}-{schema?}-{tableName}-{timestamp}.csv

Verification

• 455 tests pass (no regressions)
• 9 new test cases for blank-line splitting including CTE protection
• Lint clean