Backup classification: schema + parser + pure classifier (INERT, v0.132.0)

Task 2 of the backup-classification-redesign arc. Ships the referential-
coupling classification as DATA + PARSER + PURE CLASSIFIER, deliberately
inert — no backup tier changes behavior. Task 3 (tier policy engine) and
Task 4 (manual .fab UI) consume it.

- appbackup/classify.go: BackupSpec/BindSpec/ComposeBind/ClassifiedBind;
  ClassifyBinds (SQ5 two-level default — explicit beats :ro; unlisted
  writable→mandatory, unlisted :ro→excluded; nil spec→legacy/false);
  ValidateBackupSpec (whole-block-reject on any defect, first defect named).
- stacks/classify_binds.go: ParseComposeClassifiableBinds — ${VAR}-relative
  binds + :ro flag (NOT ParseComposeHDDMounts/ExportDataMounts, the traps).
- Metadata.Backup + LoadMetadata as the single validation choke point (bad
  catalog block → nil + one ERROR → legacy, within one sync cycle).
- Manager.ClassifiedBinds + StackDataProvider.GetStackClassifiedBinds seam
  (delegated by stackAdapter, nil-stubbed in every fake) — wired + tested
  now so Task 3 consumes a tested seam.

INERT: full pre-existing suite green with zero test-logic edits. +14 tests;
red-proofs RP-1..RP-4 confirmed. The 13 catalog backup: blocks ship in the
same app-catalog change (this controller deploys first).

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

controller/cmd/controller/main.go

@@ -1103,6 +1103,12 @@ func (a *stackAdapter) GetStackComposePath(name string) (string, bool) {
 	return s.ComposePath, true
 }
 
+// GetStackClassifiedBinds delegates to the stacks manager's backup-classification resolver (Task 2).
+// INERT — no backup tier calls this yet; wired so Task 3 consumes a tested seam.
+func (a *stackAdapter) GetStackClassifiedBinds(name string) ([]backup.ClassifiedBind, bool) {
+	return a.mgr.ClassifiedBinds(name)
+}
+
 func (a *stackAdapter) ListDeployedStacks() []backup.StackSummary {
 	var result []backup.StackSummary
 	for _, s := range a.mgr.GetStacks() {