feat: Docker 容器化、Cookie 鉴权、Coordinator 编排、FTS5 搜索与 P1-P3 全面收尾

Docker 容器化部署
  - 提供 Mode A (Alpine musl, ~23MB) 和 Mode B (Distroless glibc, ~87MB)
    两种镜像，Docker Compose 一键启动
  - build.rs 支持 SKIP_DASHBOARD_BUILD 跳过前端构建
  - 国内镜像加速 (npm/apt/apk) 通过 USE_MIRRORS build-arg 控制

  安全：Cookie-Based 鉴权系统
  - HttpOnly/SameSite=Strict Cookie 会话管理（24h 过期自动清理）
  - 登录/登出/验证接口 + 中间件注入
  - 前端登录页面 + 退出按钮
  - 三层 CORS：localhost 鉴权 / 全放通 bookmarklet / 受保护路由
  - 书签脚本 fetch 添加 credentials:'include'

  Coordinator 模式 (P2)
  - 4 个 meta-tool (delegate_task/check_task/task_stop/synthesize)
  - WorkerPool + Semaphore 并发控制 + 超时保护
  - 前端协调者模式开关

  Hook 系统：UserPromptSubmit 事件 (P2)
  - 第 13 个生命周期事件，fire-and-forget 审计

  FTS5 全文搜索 (P3)
  - agent_sessions_fts + agent_messages_fts 虚拟表
  - search_history Agent 工具 + /api/search/history HTTP 接口
  - 前端防抖搜索框 + 仅当前会话筛选

  工具加载优化 (P3)
  - defer_loading 延迟加载 (7 个重型工具)
  - is_readonly 只读标记 (9 个查询工具)
  - classifier_summary 工具目录供 LLM 按需判断

  模型回退策略 (P3)
  - LLM_FALLBACK_MODEL 优先回退 + LLM_FALLBACK_CHAIN 链式轮换
  - LlmClient model 改为 Arc<RwLock> 支持运行时切换
  - 连续 3 次过载后自动切换

  压缩记忆桥接 (P3)
  - 压缩丢弃消息 → 子代理提取持久记忆 (extract_memories_from_compaction)

  git2 依赖修复
  - 切换到 vendored-libgit2，消除 OpenSSL 系统依赖

Cargo.lock

@@ -1468,8 +1468,6 @@ dependencies = [
  "libc",
  "libgit2-sys",
  "log",
- "openssl-probe",
- "openssl-sys",
  "url",
 ]
 
@@ -2091,9 +2089,7 @@ checksum = "ee4126d8b4ee5c9d9ea891dd875cfdc1e9d0950437179104b183d7d8a74d24e8"
 dependencies = [
  "cc",
  "libc",
- "libssh2-sys",
  "libz-sys",
- "openssl-sys",
  "pkg-config",
 ]
 
@@ -2136,20 +2132,6 @@ dependencies = [
  "vcpkg",
 ]
 
-[[package]]
-name = "libssh2-sys"
-version = "0.3.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "220e4f05ad4a218192533b300327f5150e809b54c4ec83b5a1d91833601811b9"
-dependencies = [
- "cc",
- "libc",
- "libz-sys",
- "openssl-sys",
- "pkg-config",
- "vcpkg",
-]
-
 [[package]]
 name = "libz-sys"
 version = "1.1.29"
@@ -2593,24 +2575,6 @@ dependencies = [
  "syn 2.0.117",
 ]
 
-[[package]]
-name = "openssl-probe"
-version = "0.1.6"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d05e27ee213611ffe7d6348b942e8f942b37114c00cc03cec254295a4a17852e"
-
-[[package]]
-name = "openssl-sys"
-version = "0.9.117"
-source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b47e7e6bb2c38cd930d25a23b40fa52e068c10e85f3e03a7f5ba5aaca5713695"
-dependencies = [
- "cc",
- "libc",
- "pkg-config",
- "vcpkg",
-]
-
 [[package]]
 name = "outref"
 version = "0.5.2"