Add protocol HTTP application boundary.

[samuel-williams-shopify]

Summary

• Add Utopia::Application as a protocol-facing boundary that wraps Protocol::HTTP::Request into Utopia::Request and normalizes responses.
• Add lightweight Utopia::Request and Utopia::Response helpers.
• Rewrite Utopia middleware around protocol HTTP requests and responses.
• Stream static responses with Protocol::HTTP::Body::File and resolve byte ranges with Protocol::HTTP::Header::Range from protocol-http v0.67.0.

Follow-up

• Define the complete Utopia::Request#arguments contract, including form and structured arguments.
• Define and validate the complete set of supported session cookie options.
• Define duplicate and malformed request-cookie handling explicitly.

Tests

• bundle exec bake test
• 276 tests, 672 assertions.
• Decode coverage: 493/493 public definitions.