feat(ui): project drill-down route with repo-filtered event timeline

Add repo filter param to /v1/events (SQL COALESCE across payload
shapes per source). New /project/:source/* route renders a filtered
activity timeline for a single repo. Dashboard cards link to the
drill-down page.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

ui/src/pages/ProjectPage.tsx

@@ -0,0 +1,53 @@
+import { useParams } from 'react-router-dom';
+import { useQuery } from '@tanstack/react-query';
+import Col from 'react-bootstrap/Col';
+import Row from 'react-bootstrap/Row';
+import { VerticalTimeline } from 'react-vertical-timeline-component';
+
+import { fetchEvents, type Source } from '../api/client';
+import { TimelineEntry } from '../components/TimelineEntry';
+
+export function ProjectPage() {
+  const { source, '*': repoPath } = useParams();
+  const repo = repoPath ?? '';
+
+  const eventsQ = useQuery({
+    queryKey: ['project-events', source, repo],
+    queryFn: () =>
+      fetchEvents({
+        sources: source ? [source as Source] : undefined,
+        repo,
+        limit: 500,
+      }),
+    refetchInterval: 60_000,
+  });
+
+  const events = eventsQ.data ?? [];
+
+  return (
+    <>
+      <Row className="mb-3">
+        <Col>
+          <h2>{repo}</h2>
+          <small className="text-muted">{source}</small>
+        </Col>
+      </Row>
+      <Row>
+        <Col>
+          <p style={{ fontSize: '85%' }}>
+            {eventsQ.isLoading
+              ? 'loading...'
+              : eventsQ.isError
+                ? `error: ${(eventsQ.error as Error).message}`
+                : `${events.length} ${events.length === 1 ? 'activity' : 'activities'}`}
+          </p>
+          <VerticalTimeline>
+            {events.map((item) => (
+              <TimelineEntry key={item.id} item={item} />
+            ))}
+          </VerticalTimeline>
+        </Col>
+      </Row>
+    </>
+  );
+}