Add local navigation API

documentations/refactor/18-phase-10-navigation-ui.md

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+# Phase 10 Navigation UI
+
+## Purpose
+
+Phase 9 added local-first navigation APIs for seasons, weekends, sessions, and
+dataset coverage. Phase 10 should use those APIs in the React Web UI so users
+can browse ingested data instead of manually typing a `session_key`.
+
+This is a frontend slice. Keep it functional and restrained; full visual polish
+can come after the navigation workflow exists.
+
+## Scope
+
+Add React UI for:
+
+- available seasons from `/api/v1/seasons`;
+- locally ingested meetings for a selected year;
+- one weekend view from `/api/v1/weekend?meeting_key=...`;
+- session selection that routes into existing Race Hub views.
+
+The existing Race Hub analytics views should stay intact.
+
+## Product Behavior
+
+- If local data exists, users should be able to reach Race Hub without knowing a
+  raw session key.
+- Empty local database states should be explicit and calm.
+- Weekend/session rows should show dataset coverage so users understand why a
+  session may be partial.
+- Race Hub should continue accepting `session_key` in the URL for direct links.
+
+## Guardrails
+
+- Do not fetch OpenF1 directly from React.
+- Do not redesign every screen.
+- Do not remove the manual session key entry yet; keep it as a fallback.
+- Do not add a large UI framework or chart dependency.
+- Keep mobile and iPad usable.
+
+## Acceptance Criteria
+
+- Users can select a local year, meeting, and session.
+- Selecting a session opens Race Hub for that session.
+- Empty states are covered.
+- Existing Race Hub e2e tests continue passing.
+- Add focused frontend tests for navigation behavior where practical.
+- Frontend tests and build pass.