feat: fix external PDS OAuth and add client metadata endpoint
- Fix W3C DID Document parsing in discover_pds (was using PLC operation
format; plc.directory returns W3C format with different field names
and structure)
- Add protected resource metadata discovery (RFC 9728) so auth server
discovery works with Bluesky's entryway architecture
- Add DPoP nonce retry for PAR requests (bsky.social requires nonce
even for PAR)
- Add relay route GET /oauth/client-metadata.json serving AT Protocol
OAuth client metadata with dynamic client_id from public_url config
- Make wallet client_id dynamic (derived from configured relay URL)
instead of hardcoded, enabling external auth server compatibility
- Add tauri-plugin-log for iOS logging (tracing bridge via log feature)
- Add comprehensive tracing to entire claim flow (resolve, PDS auth,
verification, submission)
- Fix Secure Enclave key lookup in recovery.rs (use Reference::Key
pattern match instead of nonexistent as_sec_key method)