feat: add DAG progress dots to browse page via WebSocket events

- Add TRANSCRIPT_DAG_STATUS handler to UserEventsProvider with
  DagStatusContext and useDagStatusMap hook for live DAG task updates
- Clean up dagStatusMap entries when TRANSCRIPT_STATUS transitions
  away from "processing"
- Create DagProgressDots component rendering color-coded dots per
  DAG task (green=completed, blue pulsing=running, hollow=queued,
  red=failed, gray=cancelled) with humanized tooltip names
- Wire dagStatusMap through browse page -> TranscriptCards ->
  TranscriptStatusIcon, falling back to REST dag_status field

www/app/(app)/browse/_components/DagProgressDots.tsx

@@ -0,0 +1,61 @@
+import React from "react";
+import { Box, Flex } from "@chakra-ui/react";
+import type { DagTask } from "../../../lib/UserEventsProvider";
+
+const pulseKeyframes = `
+  @keyframes dagDotPulse {
+    0%, 100% { opacity: 1; }
+    50% { opacity: 0.3; }
+  }
+`;
+
+function humanizeTaskName(name: string): string {
+  return name
+    .split("_")
+    .map((word) => word.charAt(0).toUpperCase() + word.slice(1))
+    .join(" ");
+}
+
+function dotProps(status: DagTask["status"]): Record<string, unknown> {
+  switch (status) {
+    case "completed":
+      return { bg: "green.500" };
+    case "running":
+      return {
+        bg: "blue.500",
+        style: { animation: "dagDotPulse 1.5s ease-in-out infinite" },
+      };
+    case "failed":
+      return { bg: "red.500" };
+    case "cancelled":
+      return { bg: "gray.400" };
+    case "queued":
+    default:
+      return {
+        bg: "transparent",
+        border: "1px solid",
+        borderColor: "gray.400",
+      };
+  }
+}
+
+export default function DagProgressDots({ tasks }: { tasks: DagTask[] }) {
+  return (
+    <>
+      <style>{pulseKeyframes}</style>
+      <Flex gap="2px" alignItems="center" flexWrap="wrap">
+        {tasks.map((task) => (
+          <Box
+            key={task.name}
+            w="4px"
+            h="4px"
+            borderRadius="full"
+            flexShrink={0}
+            title={humanizeTaskName(task.name)}
+            {...dotProps(task.status)}
+          />
+        ))}
+      </Flex>
+    </>
+  );
+}