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/frontend/tests/fake-core.ts

@@ -123,6 +123,7 @@ export function makeFakeCore(overrides: Partial<Core> = {}): Core {
 			cargoTech <= 0 || targetFullMass < emptyMass
 				? null
 				: (targetFullMass - emptyMass) * cargoTech,
+		ceil3: ({ value }) => Math.ceil(Math.round(value * 1e9) / 1e6) / 1000,
 	};
 	return { ...base, ...overrides };
 }