Add SQL Preview toggle functionality and bump version to 1.0.0-nightly

[ric-v]

This pull request introduces a new feature to enable or disable the SQL Preview (Definition Viewer) in PgStudio, along with several improvements to command usability and configuration management. The changes add a user-facing toggle for the SQL Preview, update command registrations to be more robust, and enhance the UI with command icons and context-sensitive actions.

Feature: SQL Preview Enable/Disable Toggle

• Added a new configuration setting pgstudio.ddlViewer.enabled to allow users to enable or disable the SQL Preview (Definition Viewer) features and actions.
• Introduced the postgres-explorer.ddlViewer.toggleEnabled command, which can be triggered from the UI (including a new code lens and command palette) to toggle SQL Preview on or off. [1] [2] [3] [4] [5]

UI/UX Improvements

• Added icons to DDL Viewer commands for better discoverability in the command palette and menus.
• Registered DDL Viewer commands (copy, toggle, open editable copy) in the editor title bar for SQL Preview tabs, making them easily accessible when working with preview documents.

Command and Configuration Handling

• Improved command implementations to resolve the correct target tab if no URI is provided, and provide user feedback if commands are invoked without an open SQL Preview. [1] [2]
• Updated the DdlViewerService to refresh all open SQL Preview documents and code lenses when the enable/disable setting changes, ensuring the UI stays in sync with the configuration. [1] [2] [3]

Other

• Updated the extension version to 1.0.0-nightly to reflect nightly build status.