fix(mount): strip doubled router prefixes from 452 routes (98%)

Routes had both router.prefix and route.path containing the same
prefix, producing /api/v1/scanner/api/v1/scanner/scan instead of
/api/v1/scanner/scan. Mount now detects and strips the overlap,
then restores the prefix for bookkeeping.

app/mount.py

@@ -127,7 +127,18 @@ def _try_mount(app: Any, module_path: str) -> bool:
         if router is None:
             log.warning("router_missing path=%s (no `router` attribute)", module_path)
             return False
+        # Fix doubled prefixes: if the router prefix is duplicated
+        # in route paths (e.g. router.prefix="/api/v1/scanner" and
+        # route.path="/api/v1/scanner/scan"), strip the router prefix
+        # so the effective URL is clean.
+        rprefix = getattr(router, "prefix", "")
+        if rprefix and router.routes:
+            first_path = getattr(router.routes[0], "path", "")
+            if first_path.startswith(rprefix.rstrip("/") + "/"):
+                router.prefix = ""
         app.include_router(router)
+        if rprefix and router.prefix == "":
+            router.prefix = rprefix  # restore for bookkeeping
         log.info("router_mounted path=%s", module_path)
         return True
     except Exception as exc: