TanStack Query-style declarative server-state management for Relm applications.

Provides:
- Vector query key normalization and matching (exact, prefix/hierarchical)
- Optional helpers to extract URLs and query parameters from vector keys or Reitit routes
- Explicit and helper-driven cache invalidation (exact single key, hierarchical prefix, predicate, all)
- Declarative Relm `update` handlers for queries (`::update`, `::fetch`), mutations (`::mutate`), and invalidation (`::invalidate`)
- Pure context cache state reducers and Hiccup view query helpers
- Automatic stale detection, configurable retries with exponential backoff, and optimistic mutations