Implement client-side record caching and request de-duplication

[rudokemper]

Feature Request

Add client-side caching + request de-duping for record fetches to prevent repeated network calls across map clicks, gallery cards, and navigation. This improves perceived performance and reduces backend load.

User Stories & Acceptance Criteria

• As a user interacting with multiple features, I don’t want the app to re-fetch the same record repeatedly.
  • AC: Client maintains a cache keyed by _id for raw records.
  • AC: In-flight requests for the same _id are de-duped (subsequent calls await the same promise).
  • AC: Cache invalidation strategy exists and is implemented (tied to what? Let's discuss. If we can't figure it out, mark as a TODO in the code).
  • AC: Client-side caching and request de-duping behavior is covered by tests, including:
    • cache hits return data without issuing a network request,
    • concurrent requests for the same _id are de-duped and resolve from a single in-flight fetch,
    • cache invalidation correctly triggers a refetch when conditions change,
    • all tests pass in CI.

Implementation Plan

(may be added later, before work begins)