feat: auto-uppercase SQL keywords as you type

[datlechin]

Closes #660

Summary

• Add "Auto-uppercase keywords" toggle in Settings → Editor (off by default)
• When enabled, SQL keywords auto-convert to uppercase when the user types a word boundary (space, tab, newline, (, ), ,, ;)
• Keywords inside strings, comments, and backtick-quoted identifiers are left alone
• Handles backslash-escaped quotes (\') correctly
• Uses textStorage.replaceCharacters directly (not textView.replaceCharacters) to avoid CEUndoManager re-entrant assertion crash
• O(1) keyword lookup via pre-built Set<String> from SQLKeywords.keywords
• Multi-word keywords (CURRENT ROW, FORCE INDEX, USE INDEX) filtered from the set since word-boundary scanning can't match them

Test plan

• Enable setting → type select → becomes SELECT
• Type from , where , join → all uppercase
• Type inside 'select ' → NOT uppercased
• Type inside -- select → NOT uppercased
• Type inside `select` → NOT uppercased
• Type select_id → NOT uppercased (not a keyword)
• Type select( → SELECT( (parenthesis is a boundary)
• Paste select from where → NOT uppercased
• Disable setting → keywords stay as typed
• Fast typing select * from → no crash