Create Dropdown Menu for Node Tags with Filtering Functionality

To improve map organization and user control in OpenBrainMap, let's implement a dropdown menu that displays all node tags. Users should be able to check and uncheck tags in the menu to filter the map accordingly. This feature will enhance the overall usability and clarity of the mind map.

No files, tests, or entry points are named. Start by locating the map's node-tag rendering and filtering state; done means a dropdown lists all tags and checking or unchecking tags filters the map accordingly.

Written by the indexing model from the issue text.