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>

pkg/calc/number.go

@@ -0,0 +1,19 @@
+package calc
+
+import "math"
+
+// Ceil3 rounds num UP to three decimal places. The ship-class
+// calculator displays every computed value (and every goal-seek
+// back-solved input) through this so a result is never shown lower than
+// it really is — e.g. a speed of 5.0003 reads as 5.001, not 5.000, which
+// matters when a fraction of a light-year decides whether a ship clears
+// the gap to a planet. It is display-only and lives here (rather than in
+// the engine's round-to-nearest util.Fixed*) so the UI bridge can reach
+// the one implementation through WASM.
+//
+// num is pre-rounded to nine decimals before the ceil so float64
+// representation noise does not push an exact value up a step (e.g. a
+// computed 5.0 stored as 5.0000000002 stays 5.0).
+func Ceil3(num float64) float64 {
+	return math.Ceil(math.Round(num*1e9)/1e6) / 1000
+}