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/apis/skills.ts

@@ -0,0 +1,59 @@
+import { http } from "@/http"
+
+export type NodeKind = "folder" | "skill"
+
+export interface SkillNode {
+  id: number
+  parent_id: number | null
+  kind: NodeKind
+  name: string
+  path: string
+  sort_order: number
+  priority: number
+  enabled: boolean
+  published_version_no: number | null
+  latest_version_no: number | null
+  has_draft: boolean
+  updated_at: string
+}
+
+export interface SkillVersion {
+  id: number
+  version_no: number
+  content: string
+  source: "user" | "chat"
+  note: string
+  created_at: string
+}
+
+export function listSkillTree(): Promise<SkillNode[]> {
+  return http.get("/skills/tree")
+}
+
+export function createSkillNode(body: { parent_id: number | null, kind: NodeKind, name: string, priority?: number, content?: string }): Promise<SkillNode> {
+  return http.post("/skills/nodes", body)
+}
+
+export function patchSkillNode(id: number, body: { name?: string, priority?: number, enabled?: boolean }): Promise<SkillNode> {
+  return http.patch(`/skills/nodes/${id}`, body)
+}
+
+export function moveSkillNode(id: number, parentId: number | null, index: number): Promise<void> {
+  return http.post(`/skills/nodes/${id}/move`, { parent_id: parentId, index })
+}
+
+export function deleteSkillNode(id: number): Promise<void> {
+  return http.delete(`/skills/nodes/${id}`)
+}
+
+export function listSkillVersions(id: number): Promise<SkillVersion[]> {
+  return http.get(`/skills/${id}/versions`)
+}
+
+export function saveSkillDraft(id: number, content: string, note = ""): Promise<SkillVersion> {
+  return http.post(`/skills/${id}/versions`, { content, note })
+}
+
+export function publishSkillVersion(id: number, versionId: number): Promise<SkillNode> {
+  return http.post(`/skills/${id}/publish`, { version_id: versionId })
+}