fix(bitcoin): bulletproof multi-version switching (Knots & Core)

Three stacked bugs made "switch version" silently fail / crash-loop, and
the data-access mismatch corrupted a node's index during recovery attempts.

Backend renderer:
- sync_quadlet_unit ignored the per-app pinned version and re-rendered the
  quadlet with the manifest's :latest every reconcile tick, reverting any
  switch. Factor the install-time catalog/pin resolution into a shared
  resolve_catalog_image() and call it in BOTH install_fresh and
  sync_quadlet_unit.
- The renderer folded manifest `entrypoint: ["sh","-lc"]` into Exec=, which
  only worked when the image entrypoint was a passthrough shell wrapper. The
  versioned images use ENTRYPOINT ["bitcoind"], so Exec=sh -lc ... became
  `bitcoind sh -lc ...` and crash-looped. Emit a real Entrypoint= override;
  exec_changed now also compares Entrypoint=.

Images:
- Build all bitcoin images (Core + Knots, every version) as container-root
  (USER removed) like the legacy :latest image. Chain data is owned by the
  data_uid (container uid 102); root reads it via CAP_DAC_OVERRIDE (granted in
  the manifest). A non-root USER (the previous uid 1000) can't read existing
  chain data → "Error initializing block database". Still fully rootless:
  container-root maps to the unprivileged host service user.

Catalog:
- bitcoin-knots versions[]: 29.3.knots20260508/20260507/20260210 +
  29.2.knots20251110, "latest" tracking newest.
- bitcoin-core versions[]: add 29.2 + a "latest" entry. All images rebuilt
  root and published to the mirror.

Frontend:
- AppSidebar version dropdown: rename the latest option to "Always use the
  latest version" (no v prefix), fix right padding, and guarantee the current
  selection matches a real option (was rendering blank).
- New InstallVersionModal: full-screen version chooser shown from the App
  Store / Discover install button for multi-version apps (Bitcoin Knots/Core),
  app icon + "Install <name>", latest pre-selected.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

neode-ui/src/locales/en.json

@@ -330,6 +330,8 @@
   "marketplace": {
     "title": "App Store",
     "subtitle": "Discover and install apps for your new sovereign life",
+    "installModalTitle": "Install {name}",
+    "installModalHint": "Choose a version to install. The latest is recommended.",
     "curatedTab": "Curated",
     "communityTab": "Community",
     "nostrCommunityTab": "Nostr Community",
@@ -572,6 +574,7 @@
     "versionUpdates": "Version & Updates",
     "runningVersion": "Running version",
     "selectVersion": "Version",
+    "alwaysUseLatestVersion": "Always use the latest version",
     "autoUpdateLatest": "Auto-update to latest",
     "autoUpdatePinnedNote": "Auto-update is disabled while a version is pinned.",
     "confirmDowngrade": "Downgrade anyway",