feat: add server-sent events for logging and activity tracking

- Implemented a custom tracing layer (`AppLogLayer`) to capture log events and broadcast them to SSE clients.
- Created admin routes for streaming server logs and listing recent activity logs.
- Added an activity log repository interface and SQLite implementation for persisting activity events.
- Integrated activity logging into user authentication and channel CRUD operations.
- Developed frontend components for displaying server logs and activity logs in the admin panel.
- Enhanced the video player with a stats overlay for monitoring streaming metrics.

k-tv-frontend/hooks/use-admin.ts

@@ -0,0 +1,52 @@
+"use client";
+
+import { useEffect, useState } from "react";
+import { useQuery } from "@tanstack/react-query";
+import { api } from "@/lib/api";
+import type { ActivityEvent, LogLine } from "@/lib/types";
+
+const API_BASE =
+  process.env.NEXT_PUBLIC_API_URL ?? "http://localhost:4000/api/v1";
+
+export function useActivityLog(token: string | null) {
+  return useQuery<ActivityEvent[]>({
+    queryKey: ["activity-log"],
+    queryFn: () => api.admin.activity(token!),
+    enabled: !!token,
+    refetchInterval: 10_000,
+  });
+}
+
+export function useServerLogs(token: string | null) {
+  const [lines, setLines] = useState<LogLine[]>([]);
+  const [connected, setConnected] = useState(false);
+
+  useEffect(() => {
+    if (!token) return;
+
+    const url = `${API_BASE}/admin/logs?token=${encodeURIComponent(token)}`;
+    const es = new EventSource(url);
+
+    es.onopen = () => setConnected(true);
+
+    es.onmessage = (e) => {
+      try {
+        const line = JSON.parse(e.data) as LogLine;
+        setLines((prev) => [...prev.slice(-999), line]);
+      } catch {
+        // ignore malformed lines
+      }
+    };
+
+    es.onerror = () => {
+      setConnected(false);
+    };
+
+    return () => {
+      es.close();
+      setConnected(false);
+    };
+  }, [token]);
+
+  return { lines, connected };
+}