feat(ai): 创建 erp-ai crate 骨架 + 错误类型

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

Cargo.toml

@@ -16,6 +16,7 @@ members = [
     "crates/erp-plugin-freelance",
     "crates/erp-plugin-itops",
     "crates/erp-health",
+    "crates/erp-ai",
 ]
 
 [workspace.package]
@@ -81,7 +82,7 @@ validator = { version = "0.19", features = ["derive"] }
 async-trait = "0.1"
 
 # HTTP client
-reqwest = { version = "0.12", features = ["json"] }
+reqwest = { version = "0.12", features = ["json", "stream"] }
 
 # Crypto
 aes = "0.8"
@@ -100,3 +101,12 @@ erp-message = { path = "crates/erp-message" }
 erp-config = { path = "crates/erp-config" }
 erp-plugin = { path = "crates/erp-plugin" }
 erp-health = { path = "crates/erp-health" }
+erp-ai = { path = "crates/erp-ai" }
+
+# Async streaming
+futures = "0.3"
+tokio-stream = "0.1"
+async-stream = "0.3"
+
+# Template engine
+handlebars = "6"