feat(settings): move config/state to owner buckets

Add generic /api/storage config/state endpoints with merge-patch, migrate legacy YAML/JSON layout, and update UI/server to read and write owner-scoped settings. Replace config SSE events and drop /api/config routes.

packages/server/src/settings/merge-patch.ts

@@ -0,0 +1,39 @@
+type PlainObject = Record<string, unknown>
+
+export function isPlainObject(value: unknown): value is PlainObject {
+  if (!value || typeof value !== "object") return false
+  if (Array.isArray(value)) return false
+  const proto = Object.getPrototypeOf(value)
+  return proto === Object.prototype || proto === null
+}
+
+/**
+ * RFC 7396-ish merge patch with explicit null deletes.
+ * - Objects merge recursively
+ * - Arrays/scalars replace
+ * - null deletes keys
+ */
+export function applyMergePatch(current: unknown, patch: unknown): unknown {
+  if (!isPlainObject(patch)) {
+    return patch
+  }
+
+  const base: PlainObject = isPlainObject(current) ? { ...(current as PlainObject) } : {}
+
+  for (const [key, value] of Object.entries(patch)) {
+    if (value === null) {
+      delete base[key]
+      continue
+    }
+
+    const existing = base[key]
+    if (isPlainObject(value) && isPlainObject(existing)) {
+      base[key] = applyMergePatch(existing, value)
+      continue
+    }
+
+    base[key] = value
+  }
+
+  return base
+}