feat(dashboard): Recent activity events route to entity by kind

SP21 Task 2.5 — the Dashboard's 'Recent activity' card now routes clicks
to the matching entity drawer / page by event kind:

  - claim_*       → /claims?claim=<id>  (drawer in Phase 5)
  - provider_added → /providers?provider=<npi>  (ProviderDrawer)
  - remit_received → toast 'coming in a later phase' (RemitDrawer in Phase 4)
  - anything else  → toast (manual_match, unknown kinds)

Implementation:
  - New src/lib/event-routing.ts with the eventKindToUrl() helper,
    plus a unit test covering all 6 + default branches.
  - src/components/ActivityFeed.tsx gains an optional onItemClick
    prop; when set, each row gets role='button', tabIndex=0, the
    drillable hover affordance (chevron + tint), and an Enter/Space
    keybinding. e.stopPropagation() is called before the handler so a
    parent row click can't double-fire (same fix as Task 2.4).
  - src/pages/Dashboard.tsx wires the handler on the 'Recent activity'
    card via eventKindToUrl + sonner toast for unhandled kinds.
  - Backend: CycloneStore.recent_activity() now exposes claimId and
    remittanceId on each row (read from ActivityEvent.claim_id /
    remittance_id) so the routing helper has the entity ids it needs.
  - The frontend Activity interface gains optional claimId /
    remittanceId fields; the in-memory sample data and the
    addClaim store action populate them so the dashboard works in
    both API-configured and sample-data modes.

src/types/index.ts

@@ -155,6 +155,23 @@ export interface Activity {
   timestamp: string;
   npi?: string;
   amount?: number;
+  /**
+   * SP21 Task 2.5: read from the backend `ActivityEvent.claim_id` so
+   * the Dashboard "Recent activity" card can route a click on a
+   * `claim_*` event to the matching claim drawer (via
+   * `src/lib/event-routing.ts`). Populated only for events that
+   * correspond to a specific claim; `null` for orphan events such as
+   * `remit_received` or `provider_added`.
+   */
+  claimId?: string | null;
+  /**
+   * SP21 Task 2.5: read from the backend `ActivityEvent.remittance_id`.
+   * Populated only for events that reference a specific remittance
+   * (e.g. `remit_received`); `null` otherwise. The Dashboard toast
+   * covers the Phase 2 case where this routes to a not-yet-built
+   * `RemitDrawer` (Phase 4).
+   */
+  remittanceId?: string | null;
 }
 
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