Introduces an operation counter and threshold in ImageReferenceManager to trigger automatic garbage collection after a set number of canvas operations. Canvas now increments the operation count on save, undo, and redo, and exposes methods to set the operation threshold and retrieve stats including operation count. CanvasView displays the operation count and threshold after manual garbage collection.
Introduced ImageReferenceManager to track and clean up unused images from the database and cache. Added manual garbage collection controls to the UI and exposed related stats and cleanup methods in Canvas. Updated db.js with a method to retrieve all image IDs for cleanup purposes.
Refactored method and variable names from 'canvas size' to 'output area size' across multiple files for clarity. Updated UI labels and related function calls to reflect this terminology change.
Renamed Mask_tool.js to MaskTool.js and Canvas_view.js to CanvasView.js for consistency. Removed unused imports and redundant properties/methods from Canvas.js and CanvasState.js to streamline the codebase.
