fix: Add auth-context tests for reflector [b#018]

[Jenks00]

Description

This PR addresses issue #1108 for the GrantFox FWC26 campaign. It implements a simplified reflector contract alongside comprehensive tests verifying Soroban's authentication workflows, specifically capturing the signer's identity under multiple auth harnesses.

Changes Included

• Reflector Contract: Created the callora-reflector package with a single reflect_auth entrypoint.
• Strict Authorization: require_auth() is enforced on the state-changing entrypoint, capturing the caller's Address in Instance storage (StorageKey::LastSigner). No unwrap() on fallible paths.
• Auth-Context Test Suites (contracts/reflector/tests/auth.rs):
  • test_mock_all_auths: Verifies state mutations process cleanly using env.mock_all_auths().
  • test_strict_auth_harness: Uses env.mock_auths() with an exact MockAuthInvoke payload to rigorously verify the signer identity is captured correctly.
  • test_missing_auth_panics: Confirms the contract triggers a host-level auth error when no authorization is provided.
• NatSpec: Clear /// rustdoc inline documentation on all public items.

Verification

• cargo test -p callora-reflector passes with 3/3 tests passing, no failures.
• Code style aligned with repository linting configuration.

Closes #1108

[greatest0fallt1me]

Closing this as invalid — it doesn't link to a DripsWave-assigned issue or the PR author isn't the current assignee.

To contribute: apply on DripsWave, wait for assignment, then open a PR with Closes #<issue-number> in the body. Thanks!