[FuTseYi]

Changes

• Remove shared self.data mutations from the Flask image endpoint; keep the original JSON response shape for the Spring Boot client.
• Generate one unpredictable image output filename per request in the local runs/ directory; clean it up in finally.
• Do not attempt to upload a result when YOLO returned no detections or no result file, and do not report success when the result upload fails.
• Remove the previous image-route cleanup code which could remove an unrelated local file named like the URL basename.
• Add 4 dependency-free regression tests including a synchronized overlapping-request test that verifies outputs cannot overwrite one another.
• Update testing documentation with the image-only scope.

Boundaries

• This PR does not solve shared self.data / temporary path state in video and camera routes; those remain separate work.
• Does not claim real GPU/CPU inference or full Flask/Spring Boot integration testing.
• CI: Python 3.10/3.12 regressions, syntax check, Vue and Spring Boot builds.