Fix Pydantic V2 test compatibility and patch FastAPI ReDoS vulnerability

[Copilot]

Two pytest failures in CI from Pydantic V2 migration and a security vulnerability in FastAPI 0.109.0.

Changes

Test Fixes

• test_empty_messages_list: Updated assertion to accept both Pydantic V1/V2 error formats

  # Before: Expected exact string
  assert "At least one message is required" in str(exc_info.value)
  
  # After: Accept both formats
  assert "at least 1 item" in str(exc_info.value).lower() or "at least one message" in str(exc_info.value).lower()

• test_websocket_missing_required_fields: Removed incorrect pytest.raises(Exception) wrapper that expected an exception from dictionary creation. Converted to documentation test.

Security Patch

• FastAPI: 0.109.0 → 0.109.1 to patch Content-Type Header ReDoS vulnerability (CVE)

All 102 tests pass.

Original prompt

Reference: https://github.com/aztr0nutzs/perplexity_bridge_pro/actions/runs/21160352716/job/60853649956

correct the current pytest errors

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