use a single bucket rather than one per conversion

python/packages/server/src/officeconvert_server/config.py

@@ -10,6 +10,7 @@ import os
 class ServerConfig:
     """Defines environment-driven settings for server orchestration."""
 
+    s3_bucket: str
     s3_endpoint: str
     s3_access_key: str
     s3_secret_key: str
@@ -37,7 +38,11 @@ def load_server_config() -> ServerConfig:
         else s3_secure
     )
     region_env = os.getenv("S3_REGION", "").strip()
+    s3_bucket = os.getenv("S3_BUCKET", "").strip()
+    if not s3_bucket:
+        raise ValueError("S3_BUCKET is required")
     return ServerConfig(
+        s3_bucket=s3_bucket,
         s3_endpoint=os.getenv("S3_ENDPOINT", "localhost:8333"),
         s3_access_key=os.getenv("S3_ACCESS_KEY", "minioadmin"),
         s3_secret_key=os.getenv("S3_SECRET_KEY", "minioadmin"),