Implement the v1 trust directory profile

[jt55401]

Summary

• implement the canonical v1 directory routes, signing profile, content negotiation, and storage indexes
• harden HTTP signatures and direct HTTPS and did:web key resolution
• update the OpenAPI contract, conformance runner, migration script, and test matrix
• pin canonicalization 0.3.0 to merge commit 37359dd8a872f8d09fa0e7f7dd75567d92e5bec4
• replace the README with a checkout-first setup and deployment guide

Verification

• 77/77 unit tests
• OpenAPI validation with zero warnings
• 12/12 compatibility conformance fixtures
• 12/12 v1 directory smoke checks
• clean Docker test from a read-only checkout
• ShellCheck, Bash syntax, JSON parsing, YAML parsing, and git diff checks