fix: selection highlight on last line and add Execute All shortcut (#770)

[datlechin]

Summary

Closes #770 (items 2 and 3).

Selection highlight fix: The blue selection mask now correctly covers the last line when using Cmd+A or block selection. Root cause was in TextSelectionManager+FillRects.swift where rectForOffset returns nil at the document boundary, causing the last line's fill rect to be skipped entirely.

Execute All Statements (Cmd+Shift+Enter): New shortcut to run all statements in the editor sequentially, regardless of cursor position or selection. Industry-standard shortcut matching DBeaver and DataGrip. The safe mode dispatch logic was extracted from runQuery() into a shared dispatchStatements() helper to avoid duplication.

Changes

• TextSelectionManager+FillRects.swift — fallback rect at document end instead of continue
• SQLEditorView.swift — bottom content inset 0 → 8 for visual breathing room
• MainContentCoordinator+ExecuteAll.swift — new extension with runAllStatements() and extracted dispatchStatements()
• MainContentCoordinator.swift — runQuery() now calls shared dispatchStatements()
• TableProApp.swift — "Execute All Statements" menu item with Cmd+Shift+Enter
• MainContentCommandActions.swift — runAllStatements() passthrough

Test plan

• Type multi-line SQL, press Cmd+A — last line fully highlighted
• Type SELECT 1; SELECT 2; SELECT 3;, cursor on line 1, press Cmd+Shift+Enter — all 3 execute (3 result tabs)
• Same query, Cmd+Enter — only SELECT 1 executes (statement at cursor)
• Query menu shows "Execute All Statements" with Cmd+Shift+Enter
• Safe mode: Execute All respects read-only and confirmation dialogs