grid proxy: Add node slicing managment

[SalmaElsoly]

• default slicing for node
• support farmer to custom slice his node with authorization
• slice reservation

[SalmaElsoly]

work completed:

• Added node slice capacity support
• Implemented slice-aware resource filtering
• added UpdateNodeSlice DB method to update resources_cache.slice_* fields, with validation to ensure slice values don't exceed total node capacity.
• Exposed UpdateNodeSlice API endpoint
• Updated tests, mocks, and documentation
• Updated Swagger/OpenAPI docs to reflect the new API