docs(home): surface the AI pillar and add keyword home titles

Add a seventh feature card for AI Integration. It was reachable only
from the top nav despite being the platform's headline differentiator.
Also add locale keyword titles to the home pages and make the hero
image alt descriptive.

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

docs/en/index.md

@@ -1,5 +1,6 @@
 ---
 layout: home
+title: IoT DC3 · Distributed Industrial IoT Platform
 
 hero:
   name: IoT DC3
@@ -7,7 +8,7 @@ hero:
   tagline: Device connectivity, data collection, operations management, and intelligent analytics for industrial IoT. 28 multi-protocol drivers bring data up from heterogeneous devices; Spring AI lets large language models read that data and drive commands back to devices, closing the sense–decide–act–feedback loop. Distributed, multi-tenant, fully open source.
   image:
     src: /images/logo.svg
-    alt: IoT DC3
+    alt: IoT DC3 platform logo — distributed multi-protocol device connectivity and data acquisition architecture
   actions:
     - theme: brand
       text: Run your first device
@@ -32,6 +33,11 @@ features:
     details: 28 multi-protocol drivers for heterogeneous devices, with the onboarding flow and a driver capability matrix.
     link: /en/drivers/
     linkText: Browse drivers
+  - icon: 🤖
+    title: AI Integration
+    details: Spring AI brings large language models into operations — AI Agents and MCP tool calls let a model query devices, read and write points, dispatch commands, and analyze alarms.
+    link: /en/ai/
+    linkText: Explore AI
   - icon: 📚
     title: Foundations
     details: The four-layer IoT technology stack — perception, network, platform, application and security — each tied back to how DC3 implements it.

docs/zh/index.md

@@ -1,5 +1,6 @@
 ---
 layout: home
+title: IoT DC3 · 分布式工业物联网平台
 
 hero:
   name: IoT DC3
@@ -7,7 +8,7 @@ hero:
   tagline: 覆盖设备接入、数据采集、运营管理与智能分析。28 个多协议驱动接入异构设备，通过 Spring AI 让大模型读写设备数据、下发命令，形成"感知—决策—执行—反馈"闭环。分布式、多租户、全开源。
   image:
     src: /images/logo.svg
-    alt: IoT DC3
+    alt: IoT DC3 平台 logo —— 分布式多协议设备接入与数据采集架构
   actions:
     - theme: brand
       text: 跑通第一个设备
@@ -32,6 +33,11 @@ features:
     details: 28 个多协议驱动接入异构设备，含设备接入流程与驱动能力矩阵。
     link: ./drivers/
     linkText: 浏览驱动
+  - icon: 🤖
+    title: AI 集成
+    details: 基于 Spring AI 接入大语言模型，AI Agent 与 MCP 工具调用让模型查询设备、读写位号、下发命令、分析告警。
+    link: ./ai/
+    linkText: 探索 AI
   - icon: 📚
     title: 基础
     details: 物联网四层技术体系——感知、网络、平台、应用与安全，每一层都接回 DC3 怎么实现。