Fix API issues, add JWT support, improve example templates and docs

[ganiyevuz]

Summary

Fixes and improvements for the v2.0 branch:

API fixes

• RetrieveDestroyAPIView → RetrieveUpdateDestroyAPIView — OpenAPI schema now correctly shows PATCH method
• Empty PATCH validation — rejects {} with "At least one field must be provided"
• name field validation — min_length=1 prevents blank passkey names
• auth_complete_service — catches all exceptions, not just ValueError (prevents 500s from FIDO2 errors)

Example project

• Added JWT support — rest_framework_simplejwt in INSTALLED_APPS with JWTAuthentication
• Added SimpleJWT token endpoints — /api/auth/token, /api/auth/token/refresh, /api/auth/token/verify
• Added username+password login API — POST /api/auth/login returns same token format as passkey auth
• Added Swagger link to choose.html
• Fixed toggle PATCH — sends JSON with proper contentType (was sending form data)
• Fixed XSS in rest/manage.html — .html() → .text() for user-controlled key name
• Fixed typos — "Djamgo" → "Django", "Registry" → "Register"
• Fixed better error handling for duplicate passkey registration (InvalidStateError)
• Removed search bar and notification bell from navbar

Docs

• Fixed broken link in README.md (docs.Example.md → docs/Example.md)
• Fixed broken path in template-setup.md (exmple/testapp → example/test_app)

Tests

• All 52 tests pass
• 96% coverage