feat: add AI settings routes, storage, UI card, and migration

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

apps/Backend/src/ai/reminder-graph.ts

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+import { StateGraph, END, START, Annotation } from "@langchain/langgraph";
+import { ChatGoogleGenerativeAI } from "@langchain/google-genai";
+
+const GraphState = Annotation.Root({
+  message: Annotation<string>(),
+  intent: Annotation<string>(),
+  reply: Annotation<string>(),
+});
+
+type GraphStateType = typeof GraphState.State;
+
+// Keyword-based intent classifier — fast and deterministic for yes/no
+function classifyNode(state: GraphStateType) {
+  const text = state.message.toLowerCase().trim();
+
+  const yesPatterns = /\b(yes|yeah|yep|yup|sure|ok|okay|confirmed|confirm|will be there|sounds good|see you|great|perfect|absolutely|definitely)\b/;
+  const noPatterns = /\b(no|nope|can't|cannot|won't|not available|unavailable|cancel|reschedule|busy|sorry|unable|not coming|not going)\b/;
+
+  if (yesPatterns.test(text)) return { intent: "yes" };
+  if (noPatterns.test(text)) return { intent: "no" };
+  return { intent: "other" };
+}
+
+function routeByIntent(state: GraphStateType): string {
+  if (state.intent === "yes") return "thank_you";
+  if (state.intent === "no") return "reschedule";
+  return END;
+}
+
+async function thankYouNode(state: GraphStateType, config: any) {
+  const apiKey: string | undefined = config?.configurable?.apiKey;
+  const fallback = "Thank you for confirming your appointment! We look forward to seeing you.";
+
+  if (!apiKey) return { reply: fallback };
+
+  try {
+    const llm = new ChatGoogleGenerativeAI({ model: "gemini-1.5-flash", apiKey });
+    const response = await llm.invoke([
+      {
+        role: "system",
+        content:
+          "You are a friendly dental office assistant. Write a short, warm SMS reply (1-2 sentences max) thanking a patient who just confirmed their appointment. Do not add any formatting or extra text.",
+      },
+      { role: "user", content: `Patient replied: "${state.message}"` },
+    ]);
+    return { reply: String(response.content) || fallback };
+  } catch {
+    return { reply: fallback };
+  }
+}
+
+async function rescheduleNode(state: GraphStateType, config: any) {
+  const apiKey: string | undefined = config?.configurable?.apiKey;
+  const fallback = "We understand! Our assistant will contact you shortly to help reschedule.";
+
+  if (!apiKey) return { reply: fallback };
+
+  try {
+    const llm = new ChatGoogleGenerativeAI({ model: "gemini-1.5-flash", apiKey });
+    const response = await llm.invoke([
+      {
+        role: "system",
+        content:
+          "You are a friendly dental office assistant. Write a short, empathetic SMS reply (1-2 sentences max) to a patient who can't make their appointment. Tell them an assistant will contact them soon to reschedule. Do not add any formatting or extra text.",
+      },
+      { role: "user", content: `Patient replied: "${state.message}"` },
+    ]);
+    return { reply: String(response.content) || fallback };
+  } catch {
+    return { reply: fallback };
+  }
+}
+
+const graph = new StateGraph(GraphState)
+  .addNode("classify", classifyNode)
+  .addNode("thank_you", thankYouNode)
+  .addNode("reschedule", rescheduleNode)
+  .addEdge(START, "classify")
+  .addConditionalEdges("classify", routeByIntent, {
+    thank_you: "thank_you",
+    reschedule: "reschedule",
+    [END]: END,
+  })
+  .addEdge("thank_you", END)
+  .addEdge("reschedule", END)
+  .compile();
+
+export async function runReminderGraph(
+  patientMessage: string,
+  apiKey: string
+): Promise<{ reply: string | null; intent: string | null }> {
+  const result = await graph.invoke(
+    { message: patientMessage, intent: "", reply: "" },
+    { configurable: { apiKey } }
+  );
+  return {
+    reply: result.reply || null,
+    intent: result.intent || null,
+  };
+}

apps/Backend/src/routes/ai-settings.ts

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+import express, { Request, Response } from "express";
+import { storage } from "../storage";
+
+const router = express.Router();
+
+// GET /api/ai/settings
+router.get("/settings", async (req: Request, res: Response): Promise<any> => {
+  try {
+    const userId = req.user?.id;
+    if (!userId) return res.status(401).json({ message: "Unauthorized" });
+
+    const settings = await storage.getAiSettings(userId);
+    if (!settings) return res.status(200).json(null);
+
+    return res.status(200).json({ id: settings.id, apiKey: settings.apiKey });
+  } catch (err) {
+    return res.status(500).json({ error: "Failed to fetch AI settings", details: String(err) });
+  }
+});
+
+// PUT /api/ai/settings
+router.put("/settings", async (req: Request, res: Response): Promise<any> => {
+  try {
+    const userId = req.user?.id;
+    if (!userId) return res.status(401).json({ message: "Unauthorized" });
+
+    const { apiKey } = req.body;
+    if (!apiKey?.trim()) {
+      return res.status(400).json({ message: "apiKey is required" });
+    }
+
+    const settings = await storage.upsertAiSettings(userId, apiKey.trim());
+    return res.status(200).json({ id: settings.id, apiKey: settings.apiKey });
+  } catch (err) {
+    return res.status(500).json({ error: "Failed to save AI settings", details: String(err) });
+  }
+});
+
+export default router;

apps/Backend/src/storage/ai-settings-storage.ts

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+import { prisma as db } from "@repo/db/client";
+
+export const aiSettingsStorage = {
+  async getAiSettings(userId: number) {
+    return db.aiSettings.findUnique({ where: { userId } });
+  },
+
+  async upsertAiSettings(userId: number, apiKey: string) {
+    return db.aiSettings.upsert({
+      where: { userId },
+      update: { apiKey },
+      create: { userId, apiKey },
+    });
+  },
+};