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/components/ActivityFeed.tsx

@@ -1,3 +1,4 @@
+import type { KeyboardEvent, MouseEvent } from "react";
 import {
   Banknote,
   CheckCircle2,
@@ -63,9 +64,22 @@ const FALLBACK_KIND: { icon: LucideIcon; tone: string; tint: string } = {
 export function ActivityFeed({
   items,
   emptyMessage = "No activity yet.",
+  onItemClick,
 }: {
   items: Activity[];
   emptyMessage?: string;
+  /**
+   * Optional click handler for SP21 Universal Drill-Down (Task 2.5).
+   * When provided, each row becomes a clickable target: the row's
+   * outer `<li>` gets `role="button"`, `tabIndex`, the `drillable`
+   * hover affordance (chevron + tint), and an Enter/Space keybinding.
+   *
+   * `e.stopPropagation()` is called before invoking the handler so the
+   * click doesn't bubble to a hypothetical parent row click — same
+   * fix that landed on `DrillableCell` in Task 2.4. When omitted, the
+   * feed renders exactly as before (no extra DOM, no extra attrs).
+   */
+  onItemClick?: (event: Activity) => void;
 }) {
   if (items.length === 0) {
     return (
@@ -79,11 +93,36 @@ export function ActivityFeed({
       {items.map((a) => {
         const cfg = kindConfig[a.kind] ?? FALLBACK_KIND;
         const Icon = cfg.icon;
+        // SP21 Task 2.5: when a click handler is wired, the row
+        // becomes a keyboard-focusable button-like element with the
+        // drillable hover affordance. We attach the handler to the
+        // <li> directly (matching the Dashboard's existing patterns
+        // for "Top providers" / "Recent denials" rows) so the click
+        // target covers the full row width including padding.
+        const rowProps = onItemClick
+          ? {
+              role: "button" as const,
+              tabIndex: 0,
+              "aria-label": `View ${a.kind.replace(/_/g, " ")}: ${a.message}`,
+              className:
+                "drillable flex items-start gap-3 py-3 first:pt-0 last:pb-0 rounded-sm focus-visible:outline-none focus-visible:ring-2 focus-visible:ring-ring focus-visible:ring-offset-1",
+              onClick: (e: MouseEvent<HTMLLIElement>) => {
+                e.stopPropagation();
+                onItemClick(a);
+              },
+              onKeyDown: (e: KeyboardEvent<HTMLLIElement>) => {
+                if (e.key === "Enter" || e.key === " ") {
+                  e.preventDefault();
+                  e.stopPropagation();
+                  onItemClick(a);
+                }
+              },
+            }
+          : {
+              className: "flex items-start gap-3 py-3 first:pt-0 last:pb-0",
+            };
         return (
-          <li
-            key={a.id}
-            className="flex items-start gap-3 py-3 first:pt-0 last:pb-0"
-          >
+          <li key={a.id} {...rowProps}>
             <div
               className={cn(
                 "mt-0.5 h-7 w-7 shrink-0 rounded-md ring-1 ring-inset ring-border/40 flex items-center justify-center",