fix: remove bogus machineCurve default that poisoned prediction splines

The schema default for machineCurve.nq had a dummy pressure slice at
key "1" with x=[1..5] y=[10..50]. configUtils.updateConfig deep-merges
defaults into the real config, so this fake slice survived alongside the
real pressure slices (70000, 80000, ..., 390000 Pa). The predict class
then included it in its pressure-dimension spline, pulling all
interpolated y-values toward the dummy data at low pressures and
producing NEGATIVE flow predictions (e.g. -243 m³/h) where the real
curve is strictly positive.

Fix: default to empty objects {nq: {}, np: {}} so the deep merge adds
nothing. The validateMachineCurve function already returns the whole
default if the real curve is missing or invalid, so the empty default
doesn't break the no-curve-data path — it just stops poisoning the
real curve data.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/configs/rotatingMachine.json

@@ -282,42 +282,8 @@
       },
       "machineCurve": {
         "default": {
-          "nq": {
-              "1": {
-                  "x": [
-                      1,
-                      2,
-                      3,
-                      4,
-                      5
-                  ],
-                  "y": [
-                      10,
-                      20,
-                      30,
-                      40,
-                      50
-                  ]
-              }
-            },
-            "np": {
-              "1": {
-                  "x": [
-                      1,
-                      2,
-                      3,
-                      4,
-                      5
-                  ],
-                  "y": [
-                      10,
-                      20,
-                      30,
-                      40,
-                      50
-                  ]
-              }
-            }
+          "nq": {},
+          "np": {}
         },
         "rules": {
             "type": "machineCurve",