feat: load app profiles from Hana Cloud

[owjs3901]

Summary

• fetch, validate, hash-check, and cache the Hana Cloud registry and app profiles
• match focused applications across macOS, Windows, and Linux without blocking focus polling
• replace built-in PDF/music presets with remotely managed profiles and show a one-time recognition message
• validate the complete registry index boundary, including strict board metadata for the next firmware wave

Reliability and security

• fixed HTTPS origin with same-host redirects, response size limits, conditional requests, and SHA-256 verification
• content-addressed cache with rollback protection and last-known-good fallback
• background refresh/download worker; no disk or network work on the focus path

Verification

• cargo test -p hanbeon --lib (144 passed)
• cargo test -p hanbeon --test arduino (30 passed)
• cargo clippy -p hanbeon --all-targets -- -D warnings
• cargo fmt --all -- --check
• bun test (43 passed)
• bun run typecheck
• bunx oxlint
• bun run build
• independent review: Critical 0 / Important 0 / Minor 0

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