feat(extension): P2 视频页悬浮按钮 + 右键菜单 + cookie 直通；P3 侧边栏首版

- contentScripts: 仅在支持的视频平台（B 站 / YouTube / 抖音 / 快手）注入悬浮 BiliNote 按钮，点击通过 webext-bridge 发 'bilinote-start' 给 background
- background: 处理 bilinote-start 与右键菜单点击；调 /api/generate_note；写 chrome.storage；自动打开侧边栏。logic/storage 是 Vue 反应式版本，service worker 不能 import，因此把常量抽到 logic/constants.ts
- contextMenus: onInstalled 时注册"用 BiliNote 总结此视频"，限定 4 个支持平台域名
- 浏览器 Cookie 同步：options 页加按钮，按平台读 chrome.cookies.getAll，序列化为 'name=value; ...' 后 POST 给后端 /api/update_downloader_cookie。chrome.cookies + contextMenus 权限补到 manifest
- 侧边栏（P3 首版）：从 storage 读最近任务并轮询，复用 TaskProgress + MarkdownView。markmap 思维导图与 RAG 问答推到后续
- 修 P1 endpoint 拼错的 bug：/api/get_models_by_provider 实际是 /api/model_enable，404 来自这里

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

BillNote_extension/src/options/Options.vue

@@ -2,7 +2,9 @@
 import { onMounted, ref, watch } from 'vue'
 import { getModelsByProvider, getProviders, ping } from '~/logic/api'
 import { settings, settingsReady } from '~/logic/storage'
-import type { Model, Provider } from '~/logic/types'
+import { SUPPORTED_COOKIE_PLATFORMS, syncCookieToBackend } from '~/logic/cookies'
+import { PLATFORM_LABELS } from '~/logic/platform'
+import type { Model, Platform, Provider } from '~/logic/types'
 
 const providers = ref<Provider[]>([])
 const models = ref<Model[]>([])
@@ -49,6 +51,19 @@ async function testConnection() {
     : { kind: 'err', text: '无法连接后端，请检查地址、端口与 CORS 配置' }
 }
 
+const cookieStatus = ref<Record<string, { kind: 'ok' | 'err' | 'idle', text: string }>>({})
+const cookieBusy = ref<Record<string, boolean>>({})
+
+async function syncCookie(platform: Exclude<Platform, 'local'>) {
+  cookieBusy.value[platform] = true
+  cookieStatus.value[platform] = { kind: 'idle', text: '同步中…' }
+  const res = await syncCookieToBackend(platform)
+  cookieStatus.value[platform] = res.ok
+    ? { kind: 'ok', text: `已同步 ${res.count} 条 cookie ✓` }
+    : { kind: 'err', text: res.error || '同步失败' }
+  cookieBusy.value[platform] = false
+}
+
 watch(() => settings.value?.providerId, (id) => {
   if (id)
     refreshModels(id)
@@ -146,6 +161,36 @@ onMounted(async () => {
       </div>
     </section>
 
+    <section class="bg-white dark:bg-gray-800 border rounded p-4 mb-4 flex flex-col gap-3">
+      <h2 class="font-semibold">浏览器 Cookie 同步</h2>
+      <p class="text-xs text-gray-500">
+        从当前浏览器读取你已登录站点的 cookie，并写入后端 (POST /api/update_downloader_cookie)。
+        Bilibili / Douyin / Kuaishou 这类需要登录态的下载尤其需要这一步。
+      </p>
+      <div class="flex flex-col gap-2">
+        <div
+          v-for="p in SUPPORTED_COOKIE_PLATFORMS"
+          :key="p"
+          class="flex items-center justify-between gap-2 text-sm"
+        >
+          <span class="w-20">{{ PLATFORM_LABELS[p] }}</span>
+          <button class="btn-secondary" :disabled="cookieBusy[p]" @click="syncCookie(p)">
+            {{ cookieBusy[p] ? '同步中…' : '同步 Cookie' }}
+          </button>
+          <span
+            class="flex-1 text-xs"
+            :class="{
+              'text-green-700': cookieStatus[p]?.kind === 'ok',
+              'text-red-600': cookieStatus[p]?.kind === 'err',
+              'text-gray-500': cookieStatus[p]?.kind === 'idle',
+            }"
+          >
+            {{ cookieStatus[p]?.text || '' }}
+          </span>
+        </div>
+      </div>
+    </section>
+
     <p class="text-xs text-gray-500">
       所有设置自动保存。不在桌面端管理供应商/模型？请在 BiliNote web 端 (http://localhost:3015) 完成。
     </p>