fix: 架构审查修复 — broadcast、目标校验、import_csv 警告、workspace 元数据统一

- HIGH: CLI 所有修改命令补 broadcast_env_change()
- HIGH: --system/--user 互斥校验，不再静默忽略
- MEDIUM: gui/Cargo.toml 删冗余 serde_json（log 保留，lib.rs 实际使用）
- MEDIUM: import_csv 对跳过行输出 log::warn
- MEDIUM: ProfilePathEntry 从 core 重导出
- LOW: Cargo workspace.package 统一元数据

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

gui/Cargo.toml

@@ -1,11 +1,11 @@
 [package]
 name = "patheditor"
-version = "5.0.0"
 description = "Windows PATH Environment Variable Editor"
-authors = ["刘航宇"]
-license = "MIT"
-repository = "https://github.com/LHY0125/PathEditor"
-edition = "2021"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+authors.workspace = true
+repository.workspace = true
 rust-version = "1.77.2"
 
 [lib]
@@ -17,7 +17,6 @@ tauri-build = { version = "2.6.2", features = [] }
 
 [dependencies]
 path-editor-core = { path = "../core" }
-serde_json = "1.0"
 serde = { version = "1.0", features = ["derive"] }
 log = "0.4"
 tauri = { version = "2.11.2", features = [] }