SFM-Flow

This adds Advanced Item Filter Variables that can be used in White/Black lists.  Currently they only allow setting a qty, but I will expand on that in future updates.  Full change log below.

###[Added]

• Drawer Sliding Animations: Added smooth, frame-rate independent sliding animations when opening or closing the Variable Drawer.

• Interactive Handle Labels: Added a vertical "Item Vars" title label and hover tooltips directly onto the drawer's handle.

• Advanced Item Filter Nodes: Players can now instantiate a customizable variable node to save, name, and link reusable item filter configurations across the network.

• Variables Drawer UI: Added a sliding side panel containing a searchable, scrollable 3x3 grid of active variables for instant drag-and-drop capability mapping.

• Visual Warning Indicators: Canvas nodes now highlight in yellow and display custom warning tooltips when configured with empty or unassigned filter variables.

• Variable Card Item: Introduced a physical "Variable Card" carrying custom data signatures to link canvas configurations dynamically.

###[Changed]

• Centered Workspace Layout: Centered the main flowchart canvas within the screen while dynamically positioning player inventory slots to prevent layout overlaps.

• Polished Variable Drawer: Redesigned the Variable Drawer panel to use themed backgrounds, custom slots, and a tactile vertical handle.

• Extensible Panel Mappings: Upgraded the overlay menu system to support clean third-party add-on settings panel registrations.

• NBT Serialization Upgrades: Refactored behind-the-scenes save systems to safely preserve modern item components and properties.

###[Fixed]

• Coordinate Drag Drift: Fixed drag-and-drop calculation drifts that occurred when running the manager interface under custom or forced GUI scales.

• Drawer Click Blocking: Restricted the closed Variable Drawer's collision boundaries so players can interact with canvas nodes behind it without obstruction.

• Component Overlaps: Corrected inventory slot positions to ensure they never overlap with the workspace canvas or sliding drawer.

• Inventory Security Exploits: Fixed duplication vulnerabilities where virtual variable cards could be placed into player inventories or dropped as actual physical items in the world.

• Filter Serialization Recovery: Resolved an issue where variable cards would fail to persist inside external manager files when the world was reloaded.

• Item Stack Matching Desyncs: Corrected calculation issues where item transfers would occasionally fail to match due to dynamic component changes.