Bound the parsed font cache

[KickNext]

What changed

• replace the unbounded parsed OpenTypeFont map with the existing size-aware LRU cache
• retain at most 32 parsed font assets or 32 MiB of copied font bytes
• preserve concurrent-load sharing and failed-load retry behavior
• add a regression test proving the least-recently-used font is reloaded after eviction

Why

FontAssetResolver already bounded decoded glyphs, sampled shapes, and morph plans, but retained every parsed font forever. Each OpenTypeFont owns a copy of the source bytes, so apps touching many icon font assets could grow retained memory without a limit despite morphnext documenting bounded caching.

Verification

The regression test was first run against the previous implementation and failed with Expected: 2, Actual: 1 after loading 33 font assets.

Final GitHub Actions checks are green:

• Dart formatting
• Flutter analyzer with fatal infos/warnings
• 115 package tests with coverage and the 90% coverage gate
• Chrome smoke test
• example tests and release web build
• dart pub publish --dry-run
• maximum pana score gate

No public API changes.