Refactor AnimationToken for Cleaner Structure and Flexible Timing

[JaskRendix]

PR improves the AnimationToken class and related logic.

Here’s what’s changed:

• replaced NamedTuple with @dataclass for AnimationFrame, this allows future extensibility and enforces immutability with frozen=True
• refactored AnimationToken constructor and logic: cleaned up how frames are stored, removing unnecessary re-wrapping and simplified frame indexing using modulo arithmetic for looping
• added loop flag, users can now choose whether the animation repeats or plays once
• introduced done flag, signals when a non-looping animation is finished, preventing further advancement
• created update() method, allows animations to self-update based on elapsed time, making frame progression consistent regardless of frame rate or lag
• enhanced all docstrings, clear descriptions now explain purpose, parameters, return values, and behavior
• preserved __slots__, keeps memory usage optimized while the class expands in capability
• fixed typos, corrected "frames that compromise the animation" to "frames that comprise the animation"
• added simple demo: revised to showcase frame-rate-independent updates using AnimationToken.update() and loop=True, creating smoother visual transitions
• added group demo: refactored token creation and update flow to demonstrate parallel animations, using randomized positions and separated update/render cycles
• resolved broken imports by updating pyproject.toml to include the pyscroll package explicitly, fixing editable installs and restoring demo functionality during development (split out in Cleanup legacy build files and add Makefile for tooling #71)