fix: Windows-safe DB_PATH via env var, add Windows installer scripts

backend/batchtube-launcher.py

@@ -0,0 +1,34 @@
+import sys, os, time, socket, threading, webbrowser
+if getattr(sys, 'frozen', False):
+    BASE_DIR = sys._MEIPASS
+    APP_DIR = os.path.dirname(sys.executable)
+else:
+    BASE_DIR = os.path.dirname(os.path.abspath(__file__))
+    APP_DIR = BASE_DIR
+BACKEND_DIR = os.path.join(BASE_DIR,'backend') if os.path.isdir(os.path.join(BASE_DIR,'backend')) else BASE_DIR
+sys.path.insert(0, BACKEND_DIR)
+sys.path.insert(0, BASE_DIR)
+APPDATA_DIR = os.path.join(os.environ.get('APPDATA', APP_DIR), 'BatchTube')
+os.makedirs(APPDATA_DIR, exist_ok=True)
+os.environ['BATCHTUBE_DB_PATH'] = os.path.join(APPDATA_DIR, 'batchtube.db')
+for c in [os.path.join(APP_DIR,'yt-dlp.exe'), os.path.join(BASE_DIR,'yt-dlp.exe')]:
+    if os.path.exists(c): os.environ['YTDLP_PATH'] = c; break
+for d in [os.path.join(APP_DIR,'ffmpeg'), os.path.join(BASE_DIR,'ffmpeg')]:
+    if os.path.isdir(d): os.environ['PATH'] = d + os.pathsep + os.environ.get('PATH',''); break
+HOST, PORT = '127.0.0.1', 8765
+URL = f'http://{HOST}:{PORT}'
+def is_open(h, p, t=0.5):
+    try:
+        with socket.create_connection((h,p), timeout=t): return True
+    except: return False
+def open_browser():
+    for _ in range(60):
+        if is_open(HOST, PORT): time.sleep(0.3); webbrowser.open(URL); return
+        time.sleep(0.5)
+def run_server():
+    import uvicorn
+    os.chdir(BACKEND_DIR)
+    uvicorn.run('api_server:app', host=HOST, port=PORT, log_level='warning', access_log=False)
+if __name__ == '__main__':
+    threading.Thread(target=open_browser, daemon=True).start()
+    run_server()