Add MCPAuthBypassTarget for OWASP MCP-07 authentication bypass testing

[tejas0077]

Adds a new MCPAuthBypassTarget for red-teaming MCP server endpoints against authentication bypass vulnerabilities (OWASP MCP-07).

Relates to #1470

Four bypass techniques supported:

• no_auth: requests with no Authorization header
• empty_token: empty Bearer token
• malformed_token: truncated/invalid JWT
• role_escalation: tampered JWT with alg:none attack and admin role claims

Results are classified as VULNERABILITY DETECTED, SECURE, or INVESTIGATE based on the server HTTP response code.

Tests and Documentation:

• 11 unit tests covering init validation, all 4 bypass techniques, and all response scenarios
• All 11 tests passing locally
• Ruff linting clean