feat(server): add institutional memory recall

- File-based memory under .boocode/memory/ (project/user/reference topics)
- Hierarchical 4-scope scan: global → home → project → session
- Keyword/tag relevance matching for query-based recall
- Injected as <boocode-memory> block in system prompt at assembly
- v1 recall-only (extract/dream deferred to v2)

apps/server/src/services/memory/paths.ts

@@ -0,0 +1,17 @@
+import { join } from 'node:path';
+import { mkdir } from 'node:fs/promises';
+
+const TOPICS = ['project', 'user', 'reference'] as const;
+export type MemoryTopic = (typeof TOPICS)[number];
+
+export function getMemoryRoot(projectRoot: string): string {
+  return join(projectRoot, '.boocode', 'memory');
+}
+
+export function getTopicDir(root: string, topic: MemoryTopic): string {
+  return join(root, topic);
+}
+
+export async function ensureMemoryScaffold(root: string): Promise<void> {
+  await Promise.all(TOPICS.map((t) => mkdir(join(root, t), { recursive: true })));
+}