feat: add build fingerprint generation and expose it in build probe response

scripts/build_probe.py

@@ -7,12 +7,19 @@ from django.http import JsonResponse
 
 def build_probe_view(service: str):
     info_path = Path("/app/__buildinfo__.json")
+    fingerprint_path = Path("/app/__buildfingerprint__")
     info = {}
     if info_path.exists():
         try:
             info = json.loads(info_path.read_text())
         except Exception:
             info = {}
+    fingerprint = ""
+    if fingerprint_path.exists():
+        try:
+            fingerprint = fingerprint_path.read_text().strip()
+        except Exception:
+            fingerprint = ""
 
     return JsonResponse(
         {
@@ -21,6 +28,7 @@ def build_probe_view(service: str):
             "build_id": info.get("build_id", ""),
             "built_at_utc": info.get("built_at_utc", ""),
             "image_marker": info.get("image_marker", ""),
+            "fingerprint": fingerprint,
             "hostname": os.getenv("HOSTNAME", ""),
         }
     )