Add AI chat with skills management and model provider settings

- Model providers for OpenAI and Anthropic message formats (e.g. via
  Sub2API), with API keys encrypted at rest and never returned
- Skills tree with markdown editing, priorities, drafts, publishing and
  rollback; only published skills enter the chat prompt
- Chat page with tool calls over collected news and Binance USD-M
  klines, a persisted CONTEXT.md, reset, and stop-generation support
- Chat may only create skill drafts and update CONTEXT.md; publishing,
  deleting, moving and priority changes stay with the user

web/src/composables/useChatStream.ts

@@ -0,0 +1,66 @@
+import { router } from "@/router"
+
+/** POST 方式的 SSE（EventSource 只支持 GET）：逐个事件回调；stop() 断开连接，服务端随之停止生成 */
+export function useChatStream() {
+  const streaming = ref(false)
+  let controller: AbortController | null = null
+
+  async function send(body: unknown, onEvent: (name: string, data: any) => void) {
+    controller = new AbortController()
+    streaming.value = true
+    try {
+      const response = await fetch("/api/chat/messages", {
+        method: "POST",
+        headers: { "Content-Type": "application/json" },
+        body: JSON.stringify(body),
+        signal: controller.signal
+      })
+      if (response.status === 401) {
+        router.replace({ name: "login", query: { redirect: router.currentRoute.value.fullPath } })
+        return
+      }
+      if (!response.ok || !response.body) {
+        const detail = await response.json().catch(() => null)
+        onEvent("error", { message: detail?.detail ?? `请求失败：HTTP ${response.status}` })
+        return
+      }
+      const reader = response.body.pipeThrough(new TextDecoderStream()).getReader()
+      let buffer = ""
+      while (true) {
+        const { value, done } = await reader.read()
+        if (done)
+          break
+        buffer += value
+        // 事件之间以空行分隔；保留最后一段不完整的
+        const blocks = buffer.split("\n\n")
+        buffer = blocks.pop() ?? ""
+        for (const block of blocks) {
+          let name = "message"
+          let data = ""
+          for (const line of block.split("\n")) {
+            if (line.startsWith("event:"))
+              name = line.slice(6).trim()
+            else if (line.startsWith("data:"))
+              data += line.slice(5).trim()
+          }
+          // ": ping" 之类的注释行没有 data
+          if (data)
+            onEvent(name, JSON.parse(data))
+        }
+      }
+    } catch (e) {
+      if ((e as Error).name !== "AbortError")
+        onEvent("error", { message: `连接中断：${(e as Error).message}` })
+    } finally {
+      streaming.value = false
+      controller = null
+    }
+  }
+
+  function stop() {
+    controller?.abort()
+  }
+
+  onBeforeUnmount(stop)
+  return { streaming, send, stop }
+}