Update supported version to Paper 1.20.5+ (Mojang mappings required)

Author: 7yunluo

README.md

@@ -63,9 +63,11 @@ enabled-worlds:
 
 ## 环境要求
 
-- Paper 1.21+（或其 fork：Leaves、Purpur、Folia 等）
+- Paper 1.20.5+（或其 fork：Leaves、Purpur、Folia 等）
 - Java 17+
 
+> **注意**：不支持 1.20.4 及以下版本。Paper 从 1.20.5 开始使用 Mojang 映射，插件依赖此映射体系进行反射操作。
+
 ## 安全性分析
 
 | 攻击方式 | 防护等级 |

README_EN.md

@@ -63,9 +63,11 @@ enabled-worlds:
 
 ## Requirements
 
-- Paper 1.21+ (or forks: Leaves, Purpur, Folia, etc.)
+- Paper 1.20.5+ (or forks: Leaves, Purpur, Folia, etc.)
 - Java 17+
 
+> **Note**: Versions 1.20.4 and below are not supported. Paper switched to Mojang mappings starting from 1.20.5, which this plugin relies on for reflection.
+
 ## Security Analysis
 
 | Attack Vector | Protection Level |

src/main/resources/plugin.yml

@@ -1,7 +1,7 @@
 name: SeedShield
 version: 1.0.0
 main: com.seedshield.SeedShieldPlugin
-api-version: '1.21'
+api-version: '1.20'
 load: STARTUP
 description: Cryptographic structure seed protection for Paper/Spigot - prevents seed cracking
 author: yunluo7