feat: Extract hardcoded configs to environment variables

- Add environment variable configuration for backend and frontend
- Backend: DB_POOL_SIZE, JWT_EXPIRE_HOURS, timeout configs, directory paths
- Frontend: VITE_API_BASE_URL, VITE_UPLOAD_TIMEOUT, Whisper configs
- Create deployment script (scripts/deploy-backend.sh)
- Create 1Panel deployment guide (docs/1panel-deployment.md)
- Update DEPLOYMENT.md with env var documentation
- Create README.md with project overview
- Remove obsolete PRD.md, SDD.md, TDD.md (replaced by OpenSpec)
- Keep CORS allow_origins=["*"] for Electron EXE distribution

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

client/src/services/api.js

@@ -1,4 +1,5 @@
-const API_BASE_URL = "http://localhost:8000/api";
+const API_BASE_URL = import.meta.env.VITE_API_BASE_URL || "http://localhost:8000/api";
+const UPLOAD_TIMEOUT = parseInt(import.meta.env.VITE_UPLOAD_TIMEOUT || "600000", 10);
 
 let authToken = null;
 let tokenRefreshTimer = null;
@@ -351,7 +352,7 @@ export async function transcribeAudioLegacy(file, onProgress = null) {
     });
 
     xhr.open("POST", url, true);
-    xhr.timeout = 600000; // 10 minutes for large files
+    xhr.timeout = UPLOAD_TIMEOUT;
     if (token) {
       xhr.setRequestHeader("Authorization", `Bearer ${token}`);
     }