Replace live URL in tests with WireMock.Net (closes #39)

[DaraOladapo]

Summary

• Adds WireMock.Net 2.6.0 to the test project
• Replaces the hard-coded https://daraoladapo.com URL in all five test classes (GetTest, PostTest, PutTest, PatchTest, DeleteTest) with a local WireMockServer instance
• Each test class starts its own server in the constructor and disposes it via IDisposable, so tests are fully isolated and offline
• Tests now assert request headers (bearer token, custom headers, Authorization scheme+parameter) and request body content (non-empty JSON with expected fields) — not just the response type
• Each verb has at least one non-200 response path test (404, 422, 400)
• All 45 tests pass

Test plan

• dotnet build — 0 errors
• dotnet test — 45 passed, 0 failed
• No test class references a hard-coded external URL
• Covers no-auth, bearer token, custom headers, and Authorization object variants
• Verifies request body and headers, not just response type
• Covers at least one non-200 response path per HTTP verb

Closes #39

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