fix: resolve runtime errors and missing routes

- Fix $effect orphan error: move $effect calls from store constructors
  to initEffects() methods called from component context
- Fix icon rendering: create DynamicIcon component to render Lucide icons
  from name strings instead of displaying raw text
- Add /boards/new route for board creation
- Fix seed emails (admin@launcher.local / user@launcher.local) to pass
  Zod email validation

src/lib/stores/theme.svelte.ts

@@ -56,7 +56,10 @@ class ThemeStore {
 				this.#systemPreference = e.matches ? 'dark' : 'light';
 			});
 		}
+	}
 
+	/** Must be called from within a component to set up persistence and DOM effects */
+	initEffects() {
 		$effect(() => {
 			if (typeof window === 'undefined') return;
 			localStorage.setItem(THEME_STORAGE_KEY, this.mode);