Add multi-provider LLM support with model selection

- Support OpenRouter, OpenAI, and Anthropic providers
- Fetch available models after entering API key
- OpenRouter sorted by price (cheapest first)
- Store provider, model, and key per user
- Update reflections API to use selected provider/model

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/app/api/settings/route.ts

@@ -15,7 +15,9 @@ export async function GET() {
       .select({
         reminderEnabled: schema.users.reminderEnabled,
         reminderTime: schema.users.reminderTime,
-        hasLlmKey: schema.users.llmApiKey,
+        llmProvider: schema.users.llmProvider,
+        llmApiKey: schema.users.llmApiKey,
+        llmModel: schema.users.llmModel,
       })
       .from(schema.users)
       .where(eq(schema.users.id, user.id))
@@ -28,7 +30,9 @@ export async function GET() {
     return NextResponse.json({
       reminderEnabled: users[0].reminderEnabled === 1,
       reminderTime: users[0].reminderTime || "20:00",
-      hasLlmKey: Boolean(users[0].hasLlmKey),
+      llmProvider: users[0].llmProvider || null,
+      hasLlmKey: Boolean(users[0].llmApiKey),
+      llmModel: users[0].llmModel || null,
     });
   } catch (error) {
     console.error("Failed to fetch settings:", error);
@@ -55,11 +59,18 @@ export async function PATCH(request: NextRequest) {
       updates.reminderTime = body.reminderTime;
     }
 
+    if (typeof body.llmProvider === "string") {
+      updates.llmProvider = body.llmProvider || null;
+    }
+
     if (typeof body.llmApiKey === "string") {
-      // Store the API key (in production, encrypt this)
       updates.llmApiKey = body.llmApiKey || null;
     }
 
+    if (typeof body.llmModel === "string") {
+      updates.llmModel = body.llmModel || null;
+    }
+
     if (Object.keys(updates).length === 0) {
       return NextResponse.json({ error: "No updates provided" }, { status: 400 });
     }