Release v0.4.0: photographic acorn jar and easier date selection

[Dotoryman]

Summary

• Replace the fixed jar preview with a 36-stage photographic acorn scene and varied drop animation.
• Tighten the pile with deterministic collision placement, three acorn views, contact shadows, glass layering, and appropriately sized golden acorns.
• Add a dedicated date sheet with graphical calendar, validated direct entry, and quick presets.
• Update documentation and app version to 0.4.0 (build 8).

Verification

• Signed iPhone build and installation succeeded.
• 16 unit tests passed on the connected iPhone.
• Date-selection UI test and full UI test suite passed on the connected iPhone.
• Visual screenshot inspected on the connected iPhone.