Rewrite from Go + vanilla JS to Python (FastAPI) + React (TypeScript)

- Backend: Python 3.12 with FastAPI, SQLAlchemy, boto3
- Frontend: React 18 with TypeScript, Vite build tooling
- Updated Dockerfile for multi-stage Node + Python build
- Updated CI pipeline for Python backend
- Removed old Go code (cmd/, internal/, go.mod, go.sum)
- Updated README with new tech stack documentation

backend/app/config.py

@@ -0,0 +1,38 @@
+from pydantic_settings import BaseSettings
+from functools import lru_cache
+
+
+class Settings(BaseSettings):
+    # Server
+    server_host: str = "0.0.0.0"
+    server_port: int = 8080
+
+    # Database
+    database_host: str = "localhost"
+    database_port: int = 5432
+    database_user: str = "orchard"
+    database_password: str = ""
+    database_dbname: str = "orchard"
+    database_sslmode: str = "disable"
+
+    # S3
+    s3_endpoint: str = ""
+    s3_region: str = "us-east-1"
+    s3_bucket: str = "orchard-artifacts"
+    s3_access_key_id: str = ""
+    s3_secret_access_key: str = ""
+    s3_use_path_style: bool = True
+
+    @property
+    def database_url(self) -> str:
+        sslmode = f"?sslmode={self.database_sslmode}" if self.database_sslmode else ""
+        return f"postgresql://{self.database_user}:{self.database_password}@{self.database_host}:{self.database_port}/{self.database_dbname}{sslmode}"
+
+    class Config:
+        env_prefix = "ORCHARD_"
+        case_sensitive = False
+
+
+@lru_cache()
+def get_settings() -> Settings:
+    return Settings()