chore(release): prepare v0.1.5

[Shinokawa]

Summary

• Bump the Rust workspace, Flutter package, native package metadata, and prebuilt defaults to 0.1.5.
• Document tvOS support, memory-font integration, and playback starvation recovery in the changelog.
• Build and publish erika-capi-tvos.zip as a device + universal-simulator XCFramework.
• Complete the tvOS Flutter subtitle memory-font bridge and force-link the required static C ABI symbols on iOS/tvOS.
• Let OpenHarmony consume the tagged prebuilt runtime with source-build fallback and stage it beside the N-API bridge.
• Run every macOS, iOS, and tvOS CI/release build on macOS 26; cross-build macOS x64 before assembling universal artifacts.

Validation

• cargo fmt --all -- --check
• cargo test --locked -p xtask (19 passed)
• Swift parser checks for iOS and tvOS plugin sources
• Ruby syntax checks for Apple podspecs
• CI/release workflow YAML parse
• OpenHarmony CMake configure checks for both prebuilt and source paths
• flutter analyze
• flutter test (49 passed)
• git diff --check

A manual Release workflow dry-run validates all release bundles, including the new tvOS XCFramework and macOS x64 cross-build, before tagging v0.1.5.