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

Provides:
- Vector query key normalization and hierarchical matching
- Automatic URL and query parameter inference from vector keys (with optional Reitit integration)
- 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