refactor: consolidate backend into modular monolith

docs/assets/tiku-backend-architecture.svg

@@ -1,6 +1,6 @@
 <svg xmlns="http://www.w3.org/2000/svg" width="1600" height="1080" viewBox="0 0 1600 1080" role="img" aria-labelledby="title desc">
   <title id="title">TIKU Backend 当前技术架构图</title>
-  <desc id="desc">TIKU Backend 是 ASP.NET Core 模块化单体。API、Worker 和 DbMigrator 共享 Application 契约、Infrastructure 实现以及 PostgreSQL、Redis、RabbitMQ 和外部服务。</desc>
+  <desc id="desc">TIKU Backend 是 ASP.NET Core 模块化单体。API 承载 HTTP 与后台 Hosted Service，DbMigrator 负责迁移，运行时依赖 PostgreSQL、Redis 和外部服务。</desc>
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@@ -148,18 +148,18 @@
   <text class="edge-label" x="844" y="418">实现 Application 接口并操作 Domain</text>
 
   <!-- Processes -->
-  <text class="group-title" x="1318" y="129">独立运行入口</text>
+  <text class="group-title" x="1318" y="129">单体后台处理与迁移</text>
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   <rect class="node-green" x="1336" y="180" width="198" height="192" rx="6"/>
   <circle class="badge" cx="1368" cy="211" r="18"/>
-  <text class="badge-text" x="1368" y="211">W</text>
-  <text class="node-title" x="1398" y="207">Tiku.Worker</text>
+  <text class="badge-text" x="1368" y="211">BG</text>
+  <text class="node-title" x="1398" y="207">API Hosted Services</text>
   <text class="node-text" x="1354" y="242">域名 DNS / TLS 生命周期</text>
   <text class="node-text" x="1354" y="269">SaaS 订阅生命周期</text>
   <text class="node-text" x="1354" y="296">Feature 用量校准</text>
   <text class="node-text" x="1354" y="323">后台任务租约执行</text>
-  <text class="node-text" x="1354" y="350">RabbitMQ 消费者</text>
+  <text class="node-text" x="1354" y="350">与 HTTP 共用 API 进程</text>
 
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@@ -177,7 +177,7 @@
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   <!-- Data and external systems -->
-  <text class="group-title" x="48" y="773">数据、消息与外部服务</text>
+  <text class="group-title" x="48" y="773">数据与外部服务</text>
   <rect class="group" x="40" y="790" width="1520" height="212" rx="4"/>
 
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@@ -185,24 +185,24 @@
   <text class="badge-text" x="105" y="859">PG</text>
   <text class="node-title" x="139" y="854">PostgreSQL</text>
   <text class="node-text" x="92" y="892">EF Core 实体 / Identity / AuthSession</text>
-  <text class="node-text" x="92" y="917">业务数据 / BackgroundJob / Outbox</text>
+  <text class="node-text" x="92" y="917">业务数据 / BackgroundJob / Session</text>
   <text class="node-tiny" x="92" y="944">Query Filter · 写入拦截 · 数据库 Guard</text>
 
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   <circle class="badge" cx="407" cy="859" r="20"/>
   <text class="badge-text" x="407" y="859">R</text>
   <text class="node-title" x="441" y="854">Redis</text>
-  <text class="node-text" x="394" y="892">安全状态与失效广播</text>
-  <text class="node-text" x="394" y="917">分布式缓存</text>
+  <text class="node-text" x="394" y="892">安全频控</text>
+  <text class="node-text" x="394" y="917">Feature / Output Cache</text>
   <text class="node-tiny" x="394" y="944">Production 必需</text>
 
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   <circle class="badge" cx="644" cy="859" r="20"/>
-  <text class="badge-text" x="644" y="859">MQ</text>
-  <text class="node-title" x="678" y="854">RabbitMQ</text>
-  <text class="node-text" x="631" y="892">MassTransit + EF Outbox</text>
-  <text class="node-text" x="631" y="917">安全状态 / 后台任务消息</text>
-  <text class="node-tiny" x="631" y="944">API 发布 · Worker 消费</text>
+  <text class="badge-text" x="644" y="859">JOB</text>
+  <text class="node-title" x="678" y="854">PostgreSQL 任务租约</text>
+  <text class="node-text" x="631" y="892">即时任务 / RunAfter</text>
+  <text class="node-text" x="631" y="917">SKIP LOCKED / 重试</text>
+  <text class="node-tiny" x="631" y="944">API Hosted Service 执行</text>
 
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   <text class="node-title" x="890" y="856">对象存储</text>
@@ -232,5 +232,5 @@
 
   <!-- Project dependency direction -->
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-  <text class="boundary-text" x="61" y="1050">项目依赖方向：Api → Application + Infrastructure ｜ Worker → Application + Infrastructure ｜ DbMigrator → Infrastructure ｜ Infrastructure → Application + Domain + Contracts ｜ Application → Domain</text>
+  <text class="boundary-text" x="61" y="1050">项目依赖方向：Api → Application + Infrastructure ｜ DbMigrator → Infrastructure ｜ Infrastructure → Application + Domain ｜ Application → Domain</text>
 </svg>