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-server/Cargo.toml

@@ -0,0 +1,49 @@
+[package]
+name = "erp-server"
+version.workspace = true
+edition.workspace = true
+
+[[bin]]
+name = "erp-server"
+path = "src/main.rs"
+
+[dependencies]
+erp-core.workspace = true
+tokio.workspace = true
+axum.workspace = true
+tower.workspace = true
+tower-http.workspace = true
+tracing.workspace = true
+tracing-subscriber.workspace = true
+config.workspace = true
+sea-orm.workspace = true
+sqlx.workspace = true
+redis.workspace = true
+utoipa.workspace = true
+serde_json.workspace = true
+serde.workspace = true
+erp-server-migration = { path = "migration" }
+erp-auth.workspace = true
+erp-config.workspace = true
+erp-workflow.workspace = true
+erp-message.workspace = true
+erp-plugin.workspace = true
+anyhow.workspace = true
+uuid.workspace = true
+chrono.workspace = true
+moka = { version = "0.12", features = ["sync"] }
+metrics.workspace = true
+metrics-exporter-prometheus.workspace = true
+hmac = "0.12"
+sha2 = "0.10"
+hex = "0.4"
+
+[dev-dependencies]
+erp-auth = { workspace = true }
+erp-plugin = { workspace = true }
+erp-workflow = { workspace = true }
+erp-core = { workspace = true }
+async-trait.workspace = true
+futures.workspace = true
+sha2.workspace = true
+hex.workspace = true