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/prompt.ts

@@ -0,0 +1,5 @@
+export function formatMemoryBlock(entries: string[]): string {
+  if (entries.length === 0) return '';
+  const body = entries.map((e) => `- ${e}`).join('\n');
+  return `<boocode-memory>\n${body}\n</boocode-memory>`;
+}