feat(entries): encrypt template at rest, guided tour, import fixes, cleanup

Batched session work sharing app.js / index.html / Entries.pas, so it can't
split cleanly without interactive hunk staging.

- feat: encrypt `template` metadata at rest (template_enc/iv, added to
  ENCRYPTED_META_FIELDS). withEncryptedMeta skips an absent template key so
  partial re-ships (add-tag, move-to-folder) don't wipe it via LHasTemplate.
  Cleartext column kept as migration fallback. +3 unit tests.
- feat: first-run guided tour ("How it works") — spotlight + bubble, no GIFs,
  re-launchable from Settings, seen-flag in DPAPI prefs.
- fix(import): preserve original created_at on restore (was stamped to import
  time); restore entry icons on overwrite (PUT ignores icon_b64).
- fix(settings): correct clipboard-privacy copy (already excluded from Win+V);
  PIN text 4-6 -> 4-12; reorder Set-PIN above unlock-method; move tray/startup
  toggles to General; dedicated backup-password button + warning status; tab icons.
- chore: remove dead legacy monolith (app-legacy.js, index-legacy.html,
  style-legacy.css) + unused passkeyBtn stub.
- docs: full-source review (CODE_AUDIT 6b), template + favorite/pinned notes.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

js/tests/harness.js

@@ -152,6 +152,8 @@ function loadApp(overrides = {}) {
         computeStrength: (typeof computeStrength !== 'undefined' ? computeStrength : undefined),
         // merge (async, coupled — tests stub the io seams below)
         applyRemoteSnapshot, buildSyncSnapshot,
+        // metadata-at-rest
+        withEncryptedMeta, decryptEntryMeta, ENCRYPTED_META_FIELDS,
     };
     `;