F-S2 + F-S3: compose-derived appdata dir resolution (v0.131.0)

The controller assumed an app's HDD appdata dir is always appdata/<stackName>.
paperless-ngx writes appdata/paperless (stack paperless-ngx), so every consumer
keying by stack name silently missed it via a stat-and-skip. One canonical
resolver appbackup.AppDataDirNames derives the real dir name(s) from the app's
compose ${HDD_PATH} binds; all consumers use it.

- F-S2 (tier-2): RunTier2 mirrors the resolved appdata/<name> (paperless docs
  got NO tier-2 copy before). Tier2Info size + RestoreTier2Files live dir use it.
  WARN when a declared appdata dir is absent. New tier2Mirror seam.
- F-S3 (migrate, NEW): all six per-app appdata legs (collision/size/copy/verify/
  cleanup/skip-set) now loop resolved names. scope="app" migration of paperless
  previously copied nothing and left an empty media dir (scope="all" was saved by
  the merge walk). WARN on missing declared dir in the copy leg.
- Multi-dir (N>1) refusal: tier-2 backup/info/restore refuse loudly (Hungarian);
  migrate supports N. No catalog app hits it today; lifted by Task 3.
- Display: storage page sums resolved dirs.
- Truth repair: the v0.130.0 "tier-2 copies the namespace wholesale" claim is
  false; corrected in CHANGELOG + main.go export-adapter comment.

+9 tests; red-proofs RP-1..RP-5 all confirmed. Controller-only, no agent/hub
coupling. Task 1 of the backup-classification-redesign arc.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01A45Qop8YY8tS94bz63LFne

controller/internal/web/handlers.go

@@ -1675,18 +1675,28 @@ func (s *Server) appDetailsForPath(storagePath string) []StorageAppDetail {
 			Name:  stack.Meta.DisplayName,
 			Stack: stack.Meta.Slug,
 		}
-		// Try to get data size from the storage subdirectory
-		appDataDir := backup.AppDataDir(storagePath, stack.Name)
-		if fi, err := os.Stat(appDataDir); err == nil && fi.IsDir() {
-			detail.SizeHuman = dirSizeHuman(appDataDir)
+		// Try to get data size from the storage subdirectory. F-S2: the app's real appdata dir name is
+		// NOT always the stack name (paperless-ngx writes appdata/paperless) — sum the resolved dir(s).
+		// Here hddPath == storagePath (the drive's in-guest mount is the namespace root, Model A).
+		var total int64
+		var any bool
+		for _, name := range s.stackMgr.ResolveAppDataDirNames(stack.Name) {
+			d := backup.AppDataDir(storagePath, name)
+			if fi, err := os.Stat(d); err == nil && fi.IsDir() {
+				total += dirSizeBytesWalk(d)
+				any = true
+			}
+		}
+		if any {
+			detail.SizeHuman = humanizeDirBytes(total)
 		}
 		details = append(details, detail)
 	}
 	return details
 }
 
-// dirSizeHuman returns a human-readable size for a directory.
-func dirSizeHuman(path string) string {
+// dirSizeBytesWalk returns the total size in bytes of the regular files under path (0 if absent).
+func dirSizeBytesWalk(path string) int64 {
 	var total int64
 	filepath.Walk(path, func(_ string, info os.FileInfo, err error) error {
 		if err != nil || info.IsDir() {
@@ -1695,6 +1705,11 @@ func dirSizeHuman(path string) string {
 		total += info.Size()
 		return nil
 	})
+	return total
+}
+
+// humanizeDirBytes formats a byte count as B/KB/MB/GB (the storage-page display convention).
+func humanizeDirBytes(total int64) string {
 	const (
 		KB = 1024
 		MB = KB * 1024
@@ -1712,6 +1727,11 @@ func dirSizeHuman(path string) string {
 	}
 }
 
+// dirSizeHuman returns a human-readable size for a single directory.
+func dirSizeHuman(path string) string {
+	return humanizeDirBytes(dirSizeBytesWalk(path))
+}
+
 func formatFreeSpace(gb float64) string {
 	if gb >= 1000 {
 		return fmt.Sprintf("%.1f TB", gb/1024)