chore: .gitignore 보강 및 PyInstaller spec 추가

- build/, dist/, __pycache__/, .claude/, _backup/ 제외 처리
- 실행파일 빌드용 app.spec 버전 관리에 포함

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

app.spec

@@ -0,0 +1,44 @@
+# -*- mode: python ; coding: utf-8 -*-
+
+
+a = Analysis(
+    ['app.py'],
+    pathex=[],
+    binaries=[],
+    datas=[('templates', 'templates'), ('static', 'static'), ('SDK', 'SDK'), ('api_routes.py', 'api_routes.py')],
+    hiddenimports=[],
+    hookspath=[],
+    hooksconfig={},
+    runtime_hooks=[],
+    excludes=[],
+    noarchive=False,
+    optimize=0,
+)
+pyz = PYZ(a.pure)
+
+exe = EXE(
+    pyz,
+    a.scripts,
+    [],
+    exclude_binaries=True,
+    name='app',
+    debug=False,
+    bootloader_ignore_signals=False,
+    strip=False,
+    upx=True,
+    console=True,
+    disable_windowed_traceback=False,
+    argv_emulation=False,
+    target_arch=None,
+    codesign_identity=None,
+    entitlements_file=None,
+)
+coll = COLLECT(
+    exe,
+    a.binaries,
+    a.datas,
+    strip=False,
+    upx=True,
+    upx_exclude=[],
+    name='app',
+)