chore(migration): switch org to wickra-lib and maintainer email to wickra.lib@gmail.com (#59)

Introduce repo-metadata.toml as single source of truth for repo identity
(org slug, maintainer email, canonical URLs) and add sync-metadata.yml
workflow with a Python audit script that fails CI if any tracked file
drifts back to pre-migration values.

Bulk-replace across 24 tracked files:
- kingchenc/wickra -> wickra-lib/wickra (URL segment)
- kingchencp@gmail.com -> wickra.lib@gmail.com (maintainer email)
- @kingchenc -> @wickra-lib (CODEOWNERS mention only)

Person-name credits are preserved: LICENSE copyright holder, Cargo.toml
authors handle, and CHANGELOG historical @kingchenc reference all remain
unchanged. Crate / PyPI / npm package names also untouched.

Merge this PR only after the kingchenc/wickra -> wickra-lib/wickra org
transfer has happened on the GitHub side, otherwise all badges and
repository links 404 until the transfer is performed.

.github/PULL_REQUEST_TEMPLATE.md

@@ -24,9 +24,9 @@
 - [ ] New behaviour has tests; bug fixes have a regression test.
 - [ ] Public API changes are mirrored in the Python / Node / WASM bindings
       and their type stubs (If applicable).
-- [ ] The relevant page on the [project Wiki](https://github.com/kingchenc/wickra/wiki)
+- [ ] The relevant page on the [project Wiki](https://github.com/wickra-lib/wickra/wiki)
       and the `README.md` are updated (If applicable). Wiki edits go to a
-      separate repository: `https://github.com/kingchenc/wickra.wiki.git`.
+      separate repository: `https://github.com/wickra-lib/wickra.wiki.git`.
 - [ ] An entry was added under `## [Unreleased]` in `CHANGELOG.md`.
 
 ## Notes for reviewers