feat(chat): implement pull-to-refresh functionality and pagination for chat history

src/stores/chat/__tests__/chat-helpers.test.ts

@@ -3,6 +3,7 @@ import { describe, expect, it } from "vitest";
 import { ChatSendResponse } from "@/data/dto/chat";
 import type { ChatState } from "@/stores/chat/chat-state";
 import {
+  applyNetworkHistoryLoadedOutput,
   applyHttpSendOutput,
   countLockedHistoryMessages,
   localMessagesToUi,
@@ -40,6 +41,10 @@ function makeChatState(overrides: Partial<ChatState> = {}): ChatState {
     requiredCredits: 0,
     shortfallCredits: 0,
     historyLoaded: true,
+    historyTotal: 0,
+    historyLimit: 50,
+    nextHistoryOffset: 0,
+    isLoadingMoreHistory: false,
     paymentUnlockPending: false,
     unlockHistoryPromptVisible: false,
     lockedHistoryCount: 0,
@@ -244,6 +249,21 @@ describe("applyHttpSendOutput", () => {
   });
 });
 
+describe("chat history pagination helpers", () => {
+  it("falls back to the bounded history limit when the backend limit is zero", () => {
+    const nextState = applyNetworkHistoryLoadedOutput(makeChatState(), {
+      messages: [],
+      localCount: 0,
+      total: 120,
+      limit: 0,
+    });
+
+    expect(nextState.historyLimit).toBe(50);
+    expect(nextState.nextHistoryOffset).toBe(50);
+    expect(nextState.historyTotal).toBe(120);
+  });
+});
+
 describe("localMessagesToUi", () => {
   it("maps locked voice messages from history", () => {
     const [message] = localMessagesToUi([