Sync opam package metadata including x-maintenance-intent
and external dependency specifications.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Implements the WebFinger protocol (RFC 7033) for discovering information
about resources identified by URIs, and the acct URI scheme (RFC 7565)
for identifying user accounts at service providers.

Features:
- Acct module: type-safe parsing/construction of acct URIs with proper
percent-encoding per RFC 7565
- JRD module: JSON Resource Descriptor encoding/decoding using jsont
- Link module: link relation handling per RFC 7033 Section 4.4.4
- HTTP client: Eio-based WebFinger queries using requests library
- CLI tool: webfinger command for performing lookups

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>