Add S3 configuration options and improved error handling

- Add s3_verify_ssl config option for SSL/TLS verification
- Add s3_connect_timeout and s3_read_timeout config options
- Add s3_max_retries config option with adaptive retry mode
- Add S3StorageUnavailableError for backend availability issues
- Add HashCollisionError for detecting extremely rare hash collisions
- Add hash collision detection by comparing file sizes on dedup
- Handle network interruption and timeout errors explicitly
- Update routes.py to handle new exception types with appropriate HTTP codes

backend/app/config.py

@@ -22,7 +22,9 @@ class Settings(BaseSettings):
     database_pool_size: int = 5  # Number of connections to keep open
     database_max_overflow: int = 10  # Max additional connections beyond pool_size
     database_pool_timeout: int = 30  # Seconds to wait for a connection from pool
-    database_pool_recycle: int = 1800  # Recycle connections after this many seconds (30 min)
+    database_pool_recycle: int = (
+        1800  # Recycle connections after this many seconds (30 min)
+    )
 
     # S3
     s3_endpoint: str = ""
@@ -31,10 +33,16 @@ class Settings(BaseSettings):
     s3_access_key_id: str = ""
     s3_secret_access_key: str = ""
     s3_use_path_style: bool = True
+    s3_verify_ssl: bool = True  # Set to False for self-signed certs (dev only)
+    s3_connect_timeout: int = 10  # Connection timeout in seconds
+    s3_read_timeout: int = 60  # Read timeout in seconds
+    s3_max_retries: int = 3  # Max retry attempts for transient failures
 
     # Download settings
     download_mode: str = "presigned"  # "presigned", "redirect", or "proxy"
-    presigned_url_expiry: int = 3600  # Presigned URL expiry in seconds (default: 1 hour)
+    presigned_url_expiry: int = (
+        3600  # Presigned URL expiry in seconds (default: 1 hour)
+    )
 
     @property
     def database_url(self) -> str: