feat(server): add authenticated remote access and desktop bootstrap

Adds cookie-based login with a bootstrap token flow for desktop apps, secures OpenCode instance traffic with per-instance Basic auth, and updates UI/plugin clients to use credentials.

packages/server/src/auth/http-auth.ts

@@ -0,0 +1,38 @@
+import type { FastifyReply, FastifyRequest } from "fastify"
+
+export function parseCookies(header: string | undefined): Record<string, string> {
+  const result: Record<string, string> = {}
+  if (!header) return result
+
+  const parts = header.split(";")
+  for (const part of parts) {
+    const index = part.indexOf("=")
+    if (index < 0) continue
+    const key = part.slice(0, index).trim()
+    const value = part.slice(index + 1).trim()
+    if (!key) continue
+    result[key] = decodeURIComponent(value)
+  }
+  return result
+}
+
+export function isLoopbackAddress(remoteAddress: string | undefined): boolean {
+  if (!remoteAddress) return false
+  if (remoteAddress === "127.0.0.1" || remoteAddress === "::1") return true
+  if (remoteAddress === "::ffff:127.0.0.1") return true
+  return false
+}
+
+export function wantsHtml(request: FastifyRequest): boolean {
+  const accept = (request.headers["accept"] ?? "").toString().toLowerCase()
+  return accept.includes("text/html") || accept.includes("application/xhtml")
+}
+
+export function sendUnauthorized(request: FastifyRequest, reply: FastifyReply) {
+  if (request.method === "GET" && !request.url.startsWith("/api/") && wantsHtml(request)) {
+    reply.redirect("/login")
+    return
+  }
+
+  reply.code(401).send({ error: "Unauthorized" })
+}