feat: 纯文本简历按版本拆分并新增 /txt 选择页

- resume/index.txt 与 soe/index.txt 分别对应主简历与央国企简历纯文本
- /txt 改为选择页，/txt/resume 与 /txt/soe 提供对应纯文本
- 删除过时的根目录 resume.txt，Dockerfile 与 README 同步更新

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

nginx.conf

@@ -44,10 +44,25 @@ server {
         try_files $uri $uri/ /other/security-engineer/index.html;
     }
 
-    # 纯文本简历（便于复制粘贴到招聘系统）
+    # 纯文本简历选择页
     location = /txt {
+        default_type "text/html; charset=utf-8";
+        alias /usr/share/nginx/html/txt/index.html;
+    }
+
+    location = /txt/ {
+        return 301 /txt;
+    }
+
+    # 纯文本简历（便于复制粘贴到招聘系统）
+    location = /txt/resume {
         default_type "text/plain; charset=utf-8";
-        alias /usr/share/nginx/html/resume.txt;
+        alias /usr/share/nginx/html/resume/index.txt;
+    }
+
+    location = /txt/soe {
+        default_type "text/plain; charset=utf-8";
+        alias /usr/share/nginx/html/soe/index.txt;
     }
 
     # 根路径重定向到主简历