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/src/lib/calculator/ship-design-area.svelte

@@ -8,7 +8,11 @@ The component is presentational — the parent owns the state and the
 calculator math — so the ship-group upgrade flow can reuse it later.
 -->
 <script lang="ts">
-	import { i18n } from "$lib/i18n/index.svelte";
+	import { i18n, type TranslationKey } from "$lib/i18n/index.svelte";
+	import {
+		shipClassFieldErrors,
+		type ShipClassValueInvalidReason,
+	} from "$lib/util/ship-class-validation";
 	import type { ClaimedInput } from "./calc-model";
 
 	export interface DesignBlocksState {
@@ -49,6 +53,29 @@ calculator math — so the ship-group upgrade flow can reuse it later.
 		onResetTech,
 	}: Props = $props();
 
+	const VALUE_REASON_KEY: Record<ShipClassValueInvalidReason, TranslationKey> = {
+		drive_value: "game.calculator.invalid.drive_value",
+		armament_value: "game.calculator.invalid.armament_value",
+		armament_not_integer: "game.calculator.invalid.armament_not_integer",
+		weapons_value: "game.calculator.invalid.weapons_value",
+		shields_value: "game.calculator.invalid.shields_value",
+		cargo_value: "game.calculator.invalid.cargo_value",
+		armament_weapons_pair: "game.calculator.invalid.armament_weapons_pair",
+		all_zero: "game.calculator.invalid.all_zero",
+	};
+
+	// Per-block validity (independent of which one failed first) so every
+	// invalid input is highlighted, not only the first.
+	const blockErrors = $derived(shipClassFieldErrors(blocks));
+
+	function blockError(key: keyof DesignBlocksState): string {
+		const reason = blockErrors[key];
+		return reason === undefined ? "" : i18n.t(VALUE_REASON_KEY[reason]);
+	}
+	function techError(key: TechKey): string {
+		return techs[key] < 0 ? i18n.t("game.calculator.invalid.tech_value") : "";
+	}
+
 	const BLOCK_ROWS: {
 		key: keyof DesignBlocksState;
 		label: () => string;
@@ -92,6 +119,8 @@ calculator math — so the ship-group upgrade flow can reuse it later.
 					min="0"
 					bind:value={blocks[row.key]}
 					readonly={blocksReadonly}
+					aria-invalid={blockError(row.key) !== "" ? "true" : "false"}
+					title={blockError(row.key)}
 					data-testid={`calculator-block-${row.key}`}
 				/>
 			{/if}
@@ -105,6 +134,8 @@ calculator math — so the ship-group upgrade flow can reuse it later.
 						min="0"
 						bind:value={techs[techKey]}
 						oninput={() => onTechInput(techKey)}
+						aria-invalid={techError(techKey) !== "" ? "true" : "false"}
+						title={techError(techKey)}
 						data-testid={`calculator-tech-${techKey}`}
 					/>
 					{#if techOverridden[techKey]}
@@ -167,6 +198,9 @@ calculator math — so the ship-group upgrade flow can reuse it later.
 		color: #9fb0ff;
 		background: #11162a;
 	}
+	input[aria-invalid="true"] {
+		border-color: #d97a7a;
+	}
 	.tech-cell {
 		display: flex;
 		align-items: center;