feat: LAN update check on startup with notify banner (stage 2)

Read manifest.json from the configured update_source and show a dismissable
banner when a newer version is available. Notify-only — no install yet.

- services/update_service.py: version compare + check_for_update (pure, tested)
- config: add update_source key (empty = no check)
- main_window: top banner, background-thread check; open folder via os.startfile
  (QDesktopServices.openUrl mishandles file:// folder URLs — ShellExecute err 2)
- tests: +15 covering version compare and check_for_update branches
- docs 02/05/10 + tasks 17.16

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

tests/test_update_service.py

@@ -0,0 +1,105 @@
+"""Tests for services.update_service — no GUI dependency."""
+import json
+import shutil
+import sys
+import tempfile
+import unittest
+from pathlib import Path
+
+sys.path.insert(0, str(Path(__file__).parent.parent / "src"))
+
+from services.update_service import (
+    UpdateInfo,
+    check_for_update,
+    is_newer,
+    parse_version,
+)
+
+
+class TestVersionCompare(unittest.TestCase):
+    def test_parse_basic(self):
+        self.assertEqual(parse_version("1.2.3"), (1, 2, 3))
+
+    def test_parse_pads_missing_parts(self):
+        self.assertEqual(parse_version("1"), (1, 0, 0))
+        self.assertEqual(parse_version("1.5"), (1, 5, 0))
+
+    def test_parse_tolerates_suffix(self):
+        self.assertEqual(parse_version("1.2.3rc1"), (1, 2, 3))
+        self.assertEqual(parse_version("v"), (0, 0, 0))
+
+    def test_is_newer(self):
+        self.assertTrue(is_newer("1.1.0", "1.0.0"))
+        self.assertTrue(is_newer("1.0.1", "1.0.0"))
+        self.assertTrue(is_newer("2.0.0", "1.9.9"))
+
+    def test_is_not_newer(self):
+        self.assertFalse(is_newer("1.0.0", "1.0.0"))
+        self.assertFalse(is_newer("1.0.0", "1.1.0"))
+        self.assertFalse(is_newer("0.9.9", "1.0.0"))
+
+
+class TestCheckForUpdate(unittest.TestCase):
+    def setUp(self):
+        self.tmp = Path(tempfile.mkdtemp())
+
+    def tearDown(self):
+        shutil.rmtree(str(self.tmp), ignore_errors=True)
+
+    def _write_manifest(self, data):
+        with open(str(self.tmp / "manifest.json"), "w", encoding="utf-8") as f:
+            json.dump(data, f)
+
+    def test_no_source_returns_none(self):
+        self.assertIsNone(check_for_update("", "1.0.0"))
+
+    def test_missing_manifest_returns_none(self):
+        # tmp exists but has no manifest.json
+        self.assertIsNone(check_for_update(str(self.tmp), "1.0.0"))
+
+    def test_unreachable_source_returns_none(self):
+        self.assertIsNone(check_for_update(str(self.tmp / "nope"), "1.0.0"))
+
+    def test_malformed_manifest_returns_none(self):
+        with open(str(self.tmp / "manifest.json"), "w", encoding="utf-8") as f:
+            f.write("{ not valid json")
+        self.assertIsNone(check_for_update(str(self.tmp), "1.0.0"))
+
+    def test_non_object_manifest_returns_none(self):
+        self._write_manifest(["1.1.0"])
+        self.assertIsNone(check_for_update(str(self.tmp), "1.0.0"))
+
+    def test_newer_version_returns_info(self):
+        self._write_manifest({
+            "version": "1.1.0",
+            "source": r"\\nas\cmbot\releases\CMBot-1.1.0",
+            "notes": "fix batch export",
+            "mandatory": False,
+        })
+        info = check_for_update(str(self.tmp), "1.0.0")
+        self.assertIsInstance(info, UpdateInfo)
+        self.assertEqual(info.version, "1.1.0")
+        self.assertEqual(info.source, r"\\nas\cmbot\releases\CMBot-1.1.0")
+        self.assertEqual(info.notes, "fix batch export")
+        self.assertFalse(info.mandatory)
+
+    def test_same_version_returns_none(self):
+        self._write_manifest({"version": "1.0.0"})
+        self.assertIsNone(check_for_update(str(self.tmp), "1.0.0"))
+
+    def test_older_version_returns_none(self):
+        self._write_manifest({"version": "0.9.0"})
+        self.assertIsNone(check_for_update(str(self.tmp), "1.0.0"))
+
+    def test_missing_version_field_returns_none(self):
+        self._write_manifest({"notes": "no version here"})
+        self.assertIsNone(check_for_update(str(self.tmp), "1.0.0"))
+
+    def test_source_falls_back_to_update_source(self):
+        self._write_manifest({"version": "2.0.0"})   # no "source" field
+        info = check_for_update(str(self.tmp), "1.0.0")
+        self.assertEqual(info.source, str(self.tmp))
+
+
+if __name__ == "__main__":
+    unittest.main()