feat: migrate some more stuff to svelte-5, mainly app settings

app/src/lib/helpers/deepMerge.ts

@@ -0,0 +1,24 @@
+export function isObject(item: Record<string, unknown> | unknown): item is Record<string, unknown> {
+  return (typeof item === 'object' && !Array.isArray(item));
+}
+
+type Object = Record<string, unknown>;
+
+export function mergeDeep<T extends Object>(target: T, ...sources: Object[]): T {
+  if (!sources.length) return target;
+  const source = sources.shift();
+
+  if (source === undefined) return target;
+  if (isObject(target) && isObject(source)) {
+    for (const key in source) {
+      if (isObject(source[key])) {
+        if (!target[key]) Object.assign(target, { [key]: {} });
+        if (isObject(target[key])) mergeDeep(target[key], source[key]);
+      } else {
+        Object.assign(target, { [key]: source[key] });
+      }
+    }
+  }
+
+  return mergeDeep(target, ...sources);
+}

app/src/lib/helpers/localState.svelte.ts

@@ -0,0 +1,11 @@
+export function localState<T>(key: string, defaultValue: T): T {
+  const stored = localStorage.getItem(key)
+  const state = $state(stored ? JSON.parse(stored) : defaultValue)
+  $effect.root(() => {
+    $effect(() => {
+      const value = $state.snapshot(state);
+      localStorage.setItem(key, JSON.stringify(value));
+    });
+  });
+  return state;
+}