feat: add Materi section + AI agent RAG to GMW business flow

Backend:
- New materi module: schema (materi_documents table), repository, service
- ragClient: semantic + keyword search over materi docs, plus Discord
  archive via Qdrant, then LLM answer generation (RAG)
- Wire materiRouter into appRouter (list/detail/create/update/delete/chat)

Frontend:
- New types (MateriDocument, CreateMateriInput, RAG chat shapes)
- API client (SSR HTTP RPCLink + browser WS RPCLink)
- Routes: /materi list, /materi/[id] detail, /materi/new form,
  /materi/chat RAG chat UI
- Sidebar nav item 'Materi'

Migration: scripts/add-materi-documents.sql (CREATE TABLE IF NOT EXISTS)

services/backend/src/orpc/router.ts

@@ -6,6 +6,13 @@ import { chatbotService } from "../modules/chatbot/chatbot.service";
 // ── Service imports ──────────────────────────────────────────────
 import { dashboardService } from "../modules/dashboard/dashboard.service";
 import { knowledgeService } from "../modules/knowledge/knowledge.service";
+import {
+  materiQuerySchema,
+  materiRagChatSchema,
+  createMateriSchema,
+  updateMateriSchema,
+  materiService,
+} from "../modules/materi/index.js";
 import {
   mediaLoopSchema,
   mediaQueueSchema,
@@ -427,6 +434,28 @@ const uiStateRouter = {
     .handler(({ input }) => uiStateService.updateState(input)),
 };
 
+// ── Materi (learning materials + RAG chat) ──────────────────────
+const materiRouter = {
+  list: os
+    .input(materiQuerySchema)
+    .handler(({ input }) => materiService.list(input)),
+  detail: os
+    .input(z.object({ id: z.string() }))
+    .handler(({ input }) => materiService.byId(input.id)),
+  create: os
+    .input(createMateriSchema)
+    .handler(({ input }) => materiService.create(input, "anonymous")),
+  update: os
+    .input(z.object({ id: z.string() }).merge(updateMateriSchema))
+    .handler(({ input }) => materiService.update(input.id, input)),
+  delete: os
+    .input(z.object({ id: z.string() }))
+    .handler(({ input }) => materiService.delete(input.id)),
+  chat: os
+    .input(materiRagChatSchema)
+    .handler(({ input }) => materiService.ragChat(input, "anonymous")),
+};
+
 // ── Root router ───────────────────────────────────────────────────
 export const appRouter = {
   dashboard: dashboardRouter,
@@ -440,6 +469,7 @@ export const appRouter = {
   config: configRouter,
   uiState: uiStateRouter,
   knowledge: knowledgeRouter,
+  materi: materiRouter,
 };
 
 export type AppRouter = typeof appRouter;