feat(folders): nested folder tree (max depth 2) + id-based mutations

- new storeDb.ts: DB+FS layer (folders w/ parent_id, videos w/ global id)
- depth cap: sub-folder cannot have children (enforced in createFolder)
- video id: editable anytime (changeVideoId), uniqueness via PK
- routes:
  - public /folder/:topName[/:subName], /video/:topName[/:subName]/:videoId
  - admin /op/folder/:topName[/:subName], id-based /op/folders/:id/*
    and /op/videos/:id/* (rename/changeId/delete/save + idAvailable check)
- views: breadcrumb + subFolder grid; 플레이리스트 추가 button shows at 2단계
- client JS: id-based mutation endpoints, share URL data attribute,
  in-site player pushes share URL to address bar
- store.ts slimmed to Account + readAccounts (FS layer moved to storeDb)
- pickIntId accepts numeric JSON bodies

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

src/youtube.ts

@@ -4,13 +4,12 @@ import path from 'node:path'
 import { jobsDir, projectRoot } from './paths.js'
 import { upscaleOriginalTo60Fps } from './editor.js'
 import {
-  loadVideoMeta,
-  newVideoId,
-  saveVideoMeta,
-  sanitizeFolderName,
-  videoDir,
-  type VideoMeta
-} from './store.js'
+  createVideo,
+  getFolder,
+  getVideo,
+  updateVideo,
+  videoDiskDir
+} from './storeDb.js'
 
 export class YtDlpUnavailableError extends Error {
   constructor(message?: string) {
@@ -94,7 +93,7 @@ export type JobStatus = 'queued' | 'downloading' | 'done' | 'error'
 
 export interface DownloadJob {
   id: string
-  folder: string
+  folderId: number
   videoId: string
   url: string
   status: JobStatus
@@ -122,39 +121,33 @@ export function listActiveJobs(): DownloadJob[] {
 }
 
 export interface StartDownloadOpts {
-  folder: string
+  folderId: number
   url: string
   title?: string
+  /** 호출자가 영상 ID 를 지정 (플레이리스트 일괄 등록용). 미지정 시 랜덤 생성. */
+  videoId?: string
 }
 
 /** 백그라운드 yt-dlp 다운로드를 시작. videoId 도 함께 생성/저장한다. */
 export async function startYoutubeDownload(opts: StartDownloadOpts): Promise<DownloadJob> {
-  const safeFolder = sanitizeFolderName(opts.folder)
-  if (!safeFolder) throw new Error('폴더 이름이 올바르지 않습니다.')
+  const folder = getFolder(opts.folderId)
+  if (!folder) throw new Error('폴더를 찾을 수 없습니다.')
   const bin = getYtDlpPath() // 없으면 즉시 던짐
-  const videoId = newVideoId()
-  const dir = videoDir(safeFolder, videoId)
-  await fs.mkdir(dir, { recursive: true })
 
-  const now = new Date().toISOString()
-  const meta: VideoMeta = {
-    id: videoId,
+  const video = await createVideo({
+    id: opts.videoId,
+    folderId: opts.folderId,
     title: opts.title?.trim() || '제목 없음',
     originalFile: 'original.%(ext)s', // 다운로드 완료 후 실제 확장자로 갱신
-    editedFile: null,
-    durationSec: null,
     sourceType: 'youtube',
-    sourceUrl: opts.url,
-    trim: null,
-    createdAt: now,
-    updatedAt: now
-  }
-  await saveVideoMeta(safeFolder, meta)
+    sourceUrl: opts.url
+  })
 
+  const now = new Date().toISOString()
   const job: DownloadJob = {
-    id: newVideoId(),
-    folder: safeFolder,
-    videoId,
+    id: 'job-' + Math.random().toString(36).slice(2, 14),
+    folderId: opts.folderId,
+    videoId: video.id,
     url: opts.url,
     status: 'queued',
     progress: 0,
@@ -180,7 +173,7 @@ async function runJob(job: DownloadJob, bin: string): Promise<void> {
   job.message = '다운로드 시작'
   await persistJob(job)
 
-  const dir = videoDir(job.folder, job.videoId)
+  const dir = videoDiskDir(job.videoId)
   // yt-dlp 가 다운로드 후 결정한 실제 파일명을 알려주도록 --print after_move:filepath
   // 진행률은 --newline + --progress-template 으로 stdout 줄 단위 파싱.
   const args = [
@@ -288,10 +281,9 @@ async function runJob(job: DownloadJob, bin: string): Promise<void> {
         console.error('[youtube] 60fps 후처리 실패:', err)
       }
 
-      const meta = await loadVideoMeta(job.folder, job.videoId)
+      const meta = getVideo(job.videoId)
       if (meta) {
-        meta.originalFile = finalName
-        await saveVideoMeta(job.folder, meta)
+        updateVideo(job.videoId, { originalFile: finalName })
       }
       job.progress = 100
       job.status = 'done'