feat: implement incremental card caching to the server per set to prevent payload size limits.

docs/development/devlog/2025-12-16-233000_incremental_caching.md

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+# Incremental Data Caching
+
+## Objective
+Enable caching of card data to the server incrementally per set when multiple sets are selected, rather than sending a single massive payload at the end. avoiding `PayloadTooLargeError`.
+
+## Implementation Details
+1.  **Helper Function**: Created `cacheCardsToServer` helper within `fetchAndParse` to handle server communication for a chunk of cards.
+2.  **Incremental Loop**: Modified the set fetching loop to call `cacheCardsToServer` immediately after receiving data for each set.
+3.  **UI Feedback**: Updated progress text to clearly indicate when the system is "Caching [Set Name]..." to the server.
+4.  **Error Handling**: Added try/catch within the caching helper to prevent a single cache failure from aborting the entire fetch process (logs error to console).
+
+## Status
+Completed. Large multi-set fetches should now be robust against body size limits.