Release v0.4.2: place acorns on the glass floor

[Dotoryman]

Summary

• Correct the scene depth: the photographed glass floor remains behind the acorns; only the front rim and side reflections remain above them.
• Feather an oval opening in the foreground glass layer so the floor does not cover the nuts or leave a straight seam.
• Keep contact shading and bump the app to v0.4.2 (build 10).

Verification

• Signed iPhone build and installation succeeded.
• Sparse (22-day), current (257-day), and almost-full (364-day) scenes inspected on the connected iPhone using in-memory test data where applicable.
• 16 unit tests and the full UI test suite passed on the connected iPhone after the final adjustment.
• GitHub iOS CI passed.