fix(runtime): verify process ownership and path identity before terminating stored PIDs (#103)

[BerryUIKI]

Summary

Resolves #103 (F03).

• Strict Executable Ownership: Updated \ComfySupervisor, \WebUISupervisor, and \LlamaServerSupervisor\ to verify that a running process executable image strictly matches the sandboxed virtualenv Python binary (\get_python_bin()) or resides inside the engine's dedicated runtime/installation directory.
• Reject Unrelated & Recycled PIDs: Stale or recycled PIDs referencing unrelated host Python processes or system processes are identified as unowned and safely ignored without sending termination signals.
• Safe Stop & PID Cleanup: Calling \stop()\ or \get_pid()\ on an unowned or recycled PID safely unlinks the stale PID file without executing \ askkill\ or \os.kill\ on the foreign process.
• Regression Tests: Added \�ackend/tests/test_process_ownership_security.py\ testing that unrelated Python processes are rejected, stale PID files are safely cleaned, and owned runtime paths match.

Verification

• \�ackend/tests/test_process_ownership_security.py: 5/5 passed.
• Full backend pytest suite: 176/176 passed.