Add PyInstaller packaging and tufup-based auto-update pipeline

Full pipeline, verified end-to-end against the real installed tufup
0.10.0 API (initial docs/summaries turned out inaccurate in places —
e.g. the apply method is download_and_apply_update, not update;
confirmed by inspecting installed package source directly rather than
trusting docs alone):

- core/version.py: single-source app version constant.
- labdaq.spec: PyInstaller onedir build (must be onedir, not onefile —
  tufup replaces individual files in the install dir on update).
  Bundles ui/*.qss, plugins/ (needed for runtime plugin discovery), and
  repository/metadata/root.json once repo_init.py has produced one.
  Built and smoke-tested: the frozen exe launches and stays running.
- scripts/release/{repo_init,repo_release}.py: maintainer-run release
  tooling using tufup.repo.Repository, manual local signing (keys never
  touch CI). Both actually run end-to-end during development of this
  feature against a real build, not just written and assumed correct.
  Longer expiration_days than tufup-example's CI-oriented defaults
  (targets/snapshot/timestamp 90d instead of 7d/7d/1d), since we're
  signing manually, not on an automated daily schedule — see
  scripts/release/README.md for the re-signing cadence this still
  requires even between releases.
- core/updater.py: thin Client wrapper. Refuses to run outside a
  frozen build (getattr(sys, "frozen", False)) since there's no
  installed bundle for tufup to update in `python main.py` dev mode.
  Bootstraps the bundled root.json into the metadata cache dir on
  first run — tuf.ngclient.Updater loads root.json from local disk on
  construction, it does not fetch it remotely by design (the root of
  trust can't come from the same server being verified).
- core/app_settings.py: factored out app_data_dir() (was inline in
  _settings_path()) so the updater's metadata/target cache dirs live
  in the same per-user location as settings.json, deliberately outside
  the install directory an update can replace/move.
- Settings > General: version display + "Check for Updates" button,
  manual-only per discussion (no silent background network calls or
  surprise restarts for a lab-instrument-control app).

Metadata/targets are hosted on this repo's "updates" GitHub Release —
a fixed tag, not a normal per-version tag, because TUF's top-level
metadata needs a stable URL across app versions. No such GitHub-Releases-
hosting example exists in tufup or tufup-example; verified this by
fetching tufup-example's actual GitHub Actions workflow file directly
after a web search wrongly suggested one existed — the design here is
ours, not copied from upstream.

Not yet done, deliberately left for the user: running repo_init.py for
real (generates production signing keys), and creating the actual
"updates" GitHub Release. Both are irreversible-ish, security-sensitive,
externally-visible actions outside what should happen without the
user directly driving them.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

1 files changed, 10 insertions, 2 deletions

diff --git a/core/app_settings.py b/core/app_settings.py
index ea3ac49..718a768 100644
--- a/core/app_settings.py
+++ b/core/app_settings.py
@@ -18,14 +18,22 @@ import sys
 from pathlib import Path
 
 
-def _settings_path() -> Path:
+def app_data_dir() -> Path:
+    """Per-user, per-platform base directory for anything this app needs to
+    persist outside the install directory (settings, updater cache, ...) —
+    deliberately outside the install dir since an update can replace/move
+    everything in there."""
     if sys.platform == "win32":
         base = Path(os.environ.get("APPDATA", Path.home()))
     elif sys.platform == "darwin":
         base = Path.home() / "Library" / "Application Support"
     else:
         base = Path(os.environ.get("XDG_CONFIG_HOME", Path.home() / ".config"))
-    return base / "labUI" / "settings.json"
+    return base / "labUI"
+
+
+def _settings_path() -> Path:
+    return app_data_dir() / "settings.json"
 
 
 SETTINGS_PATH = _settings_path()