fix: drop netifaces (unbuildable on runner), harden build install

The packaged exe crashed with ModuleNotFoundError: No module named 'PySide6'.
Root cause: `pip install -e .` aborted because netifaces has no wheel for the
build's Python and needs MSVC to compile from source, so NO dependencies were
installed — and the workflow didn't catch it (native-command failures don't
trip $ErrorActionPreference, and the next pip command succeeded).

- Replace netifaces with a dependency-free socket-based LAN IP detection in the
  GUI; remove netifaces from pyproject and all PyInstaller specs.
- Make pip failures fatal (check $LASTEXITCODE) and add a "Verify runtime
  imports" step that fails the build before bundling if any dep is missing.

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

.gitea/workflows/build-windows.yml

@@ -87,9 +87,21 @@ jobs:
         run: |
           $ErrorActionPreference = 'Stop'
           [Net.ServicePointManager]::SecurityProtocol = [Net.SecurityProtocolType]::Tls12
+          # Native command failures do NOT trip $ErrorActionPreference, so check
+          # $LASTEXITCODE explicitly — otherwise a broken install ships silently.
           & $env:PYTHON -m pip install --upgrade pip
+          if ($LASTEXITCODE -ne 0) { throw "pip upgrade failed ($LASTEXITCODE)" }
           & $env:PYTHON -m pip install -e .
+          if ($LASTEXITCODE -ne 0) { throw "pip install -e . failed ($LASTEXITCODE)" }
           & $env:PYTHON -m pip install pyinstaller
+          if ($LASTEXITCODE -ne 0) { throw "pip install pyinstaller failed ($LASTEXITCODE)" }
+
+      - name: Verify runtime imports
+        shell: powershell
+        run: |
+          # Fail fast if any runtime dependency is missing before we bundle.
+          & $env:PYTHON -c "import PySide6.QtWidgets, fastapi, uvicorn, aiohttp, PIL, pystray, qrcode, pyautogui, pyperclip, websockets, multipart; print('deps OK')"
+          if ($LASTEXITCODE -ne 0) { throw "dependency import smoke test failed ($LASTEXITCODE)" }
 
       - name: Build Windows executable
         shell: powershell