Add read-only SQL Query dialog with syntax highlighting and export

[aa5sh]

Adds a new SQL Query dialog accessible via Logbook → SQL Query... that allows users to run custom read-only queries directly against the qlog.db SQLite database

• The editor enforces safety at the application level — only SELECT and WITH … SELECT (CTE) queries are permitted; INSERT, UPDATE, DELETE, DROP, CREATE, ALTER, ATTACH, DETACH, PRAGMA, VACUUM, and similar statements are blocked before execution
• Syntax highlighting adapts to the active light/dark theme, coloring keywords, built-in functions, string literals, numbers, comments, and known schema identifiers (tables and columns) each in a distinct color
• Intellisense-style autocomplete (Ctrl+Space, or auto-triggered after 2+ characters) offers completions for SQL keywords, built-in functions, and every table name and column name read live from the database schema
• Results are displayed in a sortable, resizable table; query execution time and row count are shown in the status bar
• Export results as TXT (tab-separated), CSV, or ADIF — the ADIF path fetches full contact records by id and routes them through the existing ExportDialog, giving identical output to the LogbookWidget right-click export
• Queries can be opened and saved as plain .sql files for easy sharing; last-used directory is remembered across sessions
• Editor supports F5 or Ctrl+Return to run, and the splitter position and window geometry are persisted between uses