feat(jp): support Japanese release assets and split APKs

[luoxiadesu]

JP catalogs use authenticated, versioned CDN paths and remote asset placeholders, while the Android release separates boot data from its resource APK. The existing international download path could not load these catalogs or supply all local data to the exporters. This change connects JP to the existing commands and exporters while preserving international configuration and cache behavior.

• Discover JP master and Android asset versions through anonymous Version metadata; download with in-memory CDN authentication, bounded refresh and origin checks.
• Read gzip catalogs and JP placeholders; bind caches, catalog records and replay tasks to the asset version/hash. Add per-region client/APK settings and support base APKs with splits, APK directories and APKS/XAPK archives, including datapack resource references.
• Select consistent JP inputs and separate default output prefixes in the music/story workflows; include resource hash in music provenance and build decisions. Document setup and support limits in docs/jp.md.

Validation:

• Local Python 3.11 suite: 1,193 passed; strict golden/object-export checks: 45 passed; final JP/catalog checks: 62 passed.
• Workflow helper tests: 66 passed, 3 skipped because external player-page and full music samples were not supplied. Pyflakes, actionlint, whitespace checks and staged Gitleaks passed; the Rust extension built in release mode.
• Live JP client 1.0.4 with local JP Android 1.0.3 data: 238 master tables downloaded and decoded; chart and jacket samples, one Live2D runtime model, and story 10753 exported. All 22 story FLAC files passed full decoding. Selected asset export produced six files and reused them offline.
• music-data --decoded-master --no-bgm: 85 songs / 340 charts, including pinned deck-model statistics, passed JSON Schema validation.

Limits: full JP story/model/movie coverage, browser playback, every BGM/jacket, and native scoring parity remain unverified. Bili chat skin rows with the JP-specific field layout still report no-value in the existing view rules. JP stories/models use a separate site from international releases. No game assets or credentials are included, and no deployment or publishing settings were changed.

Post-merge review found follow-up issues in truncated downloads, empty JP manifests and APK-only updates. The fixes are in a separate follow-up PR; they are not part of this merged commit.