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)
+}