Refactor VuIO into reusable vuio-core and thin CLI

[vyrti]

Summary

• Split the workspace into reusable vuio-core, thin vuio CLI, and oxicast.
• Move all non-CLI runtime, web, database, media, configuration, lifecycle, and platform functionality into vuio-core.
• Add host-driven runtime/configuration APIs and decompose oversized modules.
• Preserve TOML compatibility and existing integration behavior.

Validation

• cargo fmt --all -- --check
• cargo clippy --workspace --all-targets --all-features -- -D warnings
• cargo test --workspace --all-targets
• cargo build --workspace --release

The corresponding Tower integration is in vuiodev/vuio-tower#1.