feat(ui-calculator): input validation, load caps, ceil display, modernization layout

- custom load capped at cargo capacity (error when exceeded); full load shows the cargo capacity; zero cargo pins load to empty and disables the toggle

- per-input red border + tooltip for every invalid value (blocks, techs, load, MAT, modernization target); no value may be negative; locking a speed is disabled when drive is zero

- display every computed number (results + goal-seek back-solved input) rounded up to 3 decimals via a shared pkg/calc Ceil3 bridged to wasm; engine keeps its own round-to-nearest util.Fixed*

- modernization total upgrade cost spans two columns (single line)

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/core/calc/number.go

@@ -0,0 +1,10 @@
+package calc
+
+import "galaxy/calc"
+
+// Ceil3 wraps `calc.Ceil3` (`pkg/calc/number.go`): round up to three
+// decimal places. The calculator formats every displayed number through
+// this bridge so the UI and the canonical Go implementation agree.
+func Ceil3(num float64) float64 {
+	return calc.Ceil3(num)
+}

ui/core/calc/number_test.go

@@ -0,0 +1,27 @@
+package calc_test
+
+import (
+	"testing"
+
+	source "galaxy/calc"
+	bridge "galaxy/core/calc"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestCeil3Parity(t *testing.T) {
+	t.Parallel()
+	cases := []float64{0, 5, 5.0003, 4.2761, 139.29503, 0.0001, 1.9999999998}
+	for _, c := range cases {
+		assert.Equal(t, source.Ceil3(c), bridge.Ceil3(c))
+	}
+}
+
+func TestCeil3Values(t *testing.T) {
+	t.Parallel()
+	assert.Equal(t, 5.0, source.Ceil3(5.0))
+	assert.Equal(t, 5.001, source.Ceil3(5.0003))
+	assert.Equal(t, 4.277, source.Ceil3(4.2761))
+	// Float noise just above an exact step stays put.
+	assert.Equal(t, 5.0, source.Ceil3(5.0000000002))
+}