Canonicalization profile v1 across all bindings

[jt55401]

Summary

• implement the profile v1 signing pipeline across JavaScript, Go, PHP, Python, Rust, and the Rust FFI
• add strict JCS handling, parser and resource limits, key resolution hardening, and 118 shared conformance fixtures
• pin dependency graphs and test installable packages in CI
• add an isolated Docker matrix and top-down setup guides for each binding

Verification

• clean Docker matrix from empty dependency directories: JavaScript 59 tests, Go suite, PHP 133 tests with 218 assertions, Python 54 tests, Rust 22 tests, FFI 3 tests, and 118/118 fixtures in every binding
• final resolver edge fixes: JavaScript 60 tests, Go suite, and 118/118 JavaScript and Go fixtures
• package installation checks for the root and JavaScript npm packages
• gofmt, cargo fmt, ShellCheck, Bash syntax, Compose config, JSON parsing, and git diff checks