ui/phase-17: clamp ship-class name input to validator's 30-rune limit

Mirrors the validateEntityName MAX_LENGTH on the form input so the
field stops accepting characters once the limit is hit. The
validator still runs and surfaces the localised reason if a paste
overshoots; the maxlength is purely a typing-time guardrail.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/frontend/src/lib/active-view/designer-ship-class.svelte

@@ -250,6 +250,7 @@ the value fields so the diff in Phase 18 stays minimal.
 					bind:this={nameInputEl}
 					bind:value={name}
 					data-testid="designer-ship-class-input-name"
+					maxlength="30"
 					aria-invalid={validation.ok ? "false" : "true"}
 				/>
 			</label>