feat: initial project scaffold — server, client, Android APK

- FastAPI server with audio mixer (Windows + Voicemeeter), media tracking,
  notifications (progress + alerts), telemetry, and system tray .exe build
- Test suite covering notifications, audio mixer, media, telemetry, and API
- E-Ink web client (vanilla JS, DOM API, block meters, swipe gestures)
- Android WebView APK for BOOX Go 7 Color Gen II (Android 13, Kotlin)
- Design decision records in .pi/docs/design/
- PyInstaller build script for server .exe

server/build_exe.py

@@ -0,0 +1,129 @@
+"""Build script: compile PaperDash server to a standalone .exe with system tray.
+
+Usage:
+    python build_exe.py          # Build in release mode
+    python build_exe.py --debug  # Build in debug mode (with console)
+
+Output: server/dist/PaperDash.exe
+"""
+
+from __future__ import annotations
+
+import argparse
+import os
+import subprocess
+import sys
+
+SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
+DIST_DIR = os.path.join(SCRIPT_DIR, "dist")
+
+
+def build(debug: bool = False) -> None:
+    """Compile the server to an .exe using PyInstaller."""
+    os.makedirs(DIST_DIR, exist_ok=True)
+
+    # PyInstaller spec content — wraps the server with system tray
+    spec_content = f'''
+# -*- mode: python ; coding: utf-8 -*-
+"""PyInstaller spec for PaperDash with system tray."""
+
+import os
+from pathlib import Path
+
+block_cipher = None
+
+a = Analysis(
+    ["tray_wrapper.py"],
+    pathex=[],
+    binaries=[],
+    datas=[],
+    hiddenimports=[
+        "fastapi",
+        "uvicorn",
+        "pydantic",
+        "pystray",
+        "PIL",
+        "audio_mixer",
+        "media",
+        "notifications",
+        "telemetry",
+        "main",
+    ],
+    hookspath=[],
+    hooksconfig={{}},
+    runtime_hooks=[],
+    excludes=[],
+    win_no_prefer_redirects=False,
+    win_private_assemblies=False,
+    cipher=block_cipher,
+    noarchive=False,
+)
+
+pyz = PYZ(a.pure, a.zipped_data, cipher=block_cipher)
+
+exe = EXE(
+    pyz,
+    a.scripts,
+    a.binaries,
+    a.datas,
+    [],
+    name="PaperDash",
+    debug={"True": True, "False": False}[str(debug)],
+    bootloader_ignore_signals=False,
+    strip=False,
+    upx=True,
+    upx_exclude=[],
+    runtime_tmpdir=None,
+    console=False if not debug else True,
+    disable_windowed_traceback=False,
+    argv_emulation=False,
+    target_arch=None,
+    codesign_identity=None,
+    entitlements_file=None,
+    icon=None,
+)
+'''
+
+    spec_path = os.path.join(SCRIPT_DIR, "PaperDash.spec")
+    with open(spec_path, "w") as f:
+        f.write(spec_content)
+
+    try:
+        cmd = [
+            sys.executable,
+            "-m",
+            "PyInstaller",
+            spec_path,
+            "--clean",
+        ]
+        if debug:
+            cmd.append("--debug=all")
+
+        print(f"Building PaperDash.exe (debug={debug})...")
+        print(f"  Spec: {spec_path}")
+        print(f"  Output: {DIST_DIR}/PaperDash.exe")
+        print()
+
+        subprocess.run(cmd, check=True)
+
+        exe_path = os.path.join(DIST_DIR, "PaperDash.exe")
+        if os.path.exists(exe_path):
+            size_mb = os.path.getsize(exe_path) / (1024 * 1024)
+            print(f"\nBuild complete: {exe_path} ({size_mb:.1f} MB)")
+        else:
+            print("\nBuild completed but .exe not found in dist/")
+
+    except subprocess.CalledProcessError as e:
+        print(f"\nBuild failed: {e}", file=sys.stderr)
+        sys.exit(1)
+    finally:
+        # Clean up spec file
+        if os.path.exists(spec_path):
+            os.remove(spec_path)
+
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Build PaperDash .exe")
+    parser.add_argument("--debug", action="store_true", help="Build with debug console")
+    args = parser.parse_args()
+    build(debug=args.debug)