v2 host: portable desktop app (tray + FastAPI + WebView2 panel), unified config, HA control

Fold the Windows tray/daemon into one self-contained Clawdmeter.exe with a
settings UI, and wire the host side of the watch features:

- config.py: single %LOCALAPPDATA%\Clawdmeter\config.json (ha/buttons/settings),
  atomic writes, auto-migration from the old ha_config.json.
- server.py: local FastAPI (127.0.0.1:8723) — GET/PUT /api/config (token masked),
  POST /api/ha/test, GET /api/ha/entities, GET /api/status.
- web/index.html: brand-styled settings panel (Status/HA/Buttons/Settings tabs).
- panel.py: pywebview/WebView2 window, launched as its own process (pywebview and
  pystray both want the main thread); tray "Settings" opens it via --panel.
- daemon: HA command dispatch (toggle/bri/ct), dynamic button labels + index→
  action mapping, watch-battery low warning toast, and the dimmer "dim" snapshot
  (dimreq → light_snapshot of the first entity) so the watch dial seeds from HA.
- clawdmeter.spec / requirements: bundle fastapi+uvicorn+pywebview+webview backend.
- build-exe.ps1: ASCII-only (Windows PowerShell 5.1 mangles em-dashes under cp1251).

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

build-exe.ps1

@@ -1,4 +1,4 @@
-# build-exe.ps1 — build the standalone Clawdmeter.exe (PyInstaller).
+# build-exe.ps1 - build the standalone Clawdmeter.exe (PyInstaller).
 #
 # Produces dist\Clawdmeter.exe: a single self-contained tray + daemon executable
 # that runs on ANY Windows 11 machine with no Python install and no pip. Build it
@@ -26,7 +26,7 @@ Log "=== Clawdmeter exe build ==="
 if (-not (Test-Path $PythonExe)) {
     Log "Creating virtual environment at .venv ..."
     & python -m venv $VenvDir
-    if ($LASTEXITCODE -ne 0) { throw "venv creation failed (exit $LASTEXITCODE) — is Python on PATH?" }
+    if ($LASTEXITCODE -ne 0) { throw "venv creation failed (exit $LASTEXITCODE) - is Python on PATH?" }
 }
 
 # 2. Runtime dependencies + PyInstaller (the only build-time extra)
@@ -45,4 +45,4 @@ $ExePath = Join-Path $RepoRoot "dist\Clawdmeter.exe"
 if (-not (Test-Path $ExePath)) { throw "Build reported success but $ExePath is missing" }
 $sizeMB = [math]::Round((Get-Item $ExePath).Length / 1MB, 1)
 Log "Build complete: $ExePath ($sizeMB MB)"
-Log "Distribute this exe via a Gitea release — it is intentionally not committed to git."
+Log "Distribute this exe via a Gitea release - it is intentionally not committed to git."