feat: initialize ERP base platform (extracted from HMS)

- Stripped 11 business crates (health, ai, dialysis, plugins)
- Cleaned AppState, AppConfig, main.rs from business coupling
- Reduced migrations from 169 to 53 (base-only)
- Removed health_provider trait from erp-core
- Removed business integration tests
- Removed gateway rate limiting middleware
- Base capabilities: auth, RBAC, JWT, config, workflow, message, plugin, audit, crypto, RLS, multi-tenant

Cargo check: OK
Cargo test: OK

crates/erp-message/Cargo.toml

@@ -0,0 +1,23 @@
+[package]
+name = "erp-message"
+version.workspace = true
+edition.workspace = true
+
+[dependencies]
+erp-core.workspace = true
+tokio = { workspace = true, features = ["full"] }
+serde = { workspace = true, features = ["derive"] }
+serde_json = { workspace = true }
+uuid = { workspace = true, features = ["v7", "serde"] }
+chrono = { workspace = true, features = ["serde"] }
+axum = { workspace = true }
+sea-orm = { workspace = true, features = ["sqlx-postgres", "runtime-tokio-rustls", "with-uuid", "with-chrono", "with-json"] }
+tracing = { workspace = true }
+anyhow.workspace = true
+thiserror.workspace = true
+utoipa = { workspace = true, features = ["uuid", "chrono"] }
+async-trait.workspace = true
+validator.workspace = true
+futures.workspace = true
+tokio-stream.workspace = true
+async-stream.workspace = true