feat: complete Phase 1 infrastructure

- erp-core: error types, shared types, event bus, ErpModule trait
- erp-server: config loading, database/Redis connections, migrations
- erp-server/migration: tenants table with SeaORM
- apps/web: Vite + React 18 + TypeScript + Ant Design 5 + TailwindCSS
- Web frontend: main layout with sidebar, header, routing
- Docker: PostgreSQL 16 + Redis 7 development environment
- All workspace crates compile successfully (cargo check passes)

crates/erp-server/migration/src/lib.rs

@@ -0,0 +1,12 @@
+pub use sea_orm_migration::prelude::*;
+
+mod m20260410_000001_create_tenant;
+
+pub struct Migrator;
+
+#[async_trait::async_trait]
+impl MigratorTrait for Migrator {
+    fn migrations() -> Vec<Box<dyn MigrationTrait>> {
+        vec![Box::new(m20260410_000001_create_tenant::Migration)]
+    }
+}