Add Simfinity.js to JavaScript server libraries

src/code/language-support/javascript/server/simfinity-js.md

@@ -0,0 +1,46 @@
+---
+name: Simfinity.js
+description: Generate GraphQL queries, CRUD mutations, relationships, and database storage from GraphQL object types, with MongoDB/Mongoose or PostgreSQL adapters.
+url: https://simtlix.github.io/simfinity.js/
+github: simtlix/simfinity.js
+npm: "@simtlix/simfinity-js"
+tags:
+  - tools-and-libraries
+  - backend
+---
+
+Simfinity.js starts with types defined using `GraphQLObjectType` from the `graphql` package. Register those types to generate a database-backed schema, then serve it with a GraphQL server such as Yoga. Relationship metadata connects nested API operations to database relationships.
+
+The MongoDB adapter uses Mongoose. The PostgreSQL adapter uses native PostgreSQL tables, UUID identities, and foreign-key constraints. Both share a runtime for validation, controllers, query scopes, lifecycle hooks, and authorization rules. Authentication and trusted request context remain part of the application.
+
+For example, register an entity with the PostgreSQL adapter:
+
+```js
+import {
+  GraphQLID,
+  GraphQLNonNull,
+  GraphQLObjectType,
+  GraphQLString,
+} from "graphql"
+import pg from "pg"
+import { createPostgres } from "@simtlix/simfinity-postgres"
+
+const SerieType = new GraphQLObjectType({
+  name: "Serie",
+  fields: {
+    id: { type: GraphQLID },
+    name: { type: new GraphQLNonNull(GraphQLString) },
+  },
+})
+
+const pool = new pg.Pool({ connectionString: process.env.DATABASE_URL })
+const simfinity = createPostgres({ pool, schema: "series_api" })
+
+simfinity.connect(null, SerieType, "serie", "series")
+const schema = simfinity.createSchema()
+await simfinity.initializeDatabase({ mode: "create" })
+```
+
+The [PostgreSQL quick start](https://simtlix.github.io/simfinity.js/guide/postgresql.html) includes a complete runnable server and a series/season example with nested writes. Database initialization is explicit; schema evolution requires deliberate migrations.
+
+The optional [MCP integration](https://simtlix.github.io/simfinity.js/guide/mcp.html) exposes selected GraphQL operations as tools and works with either database adapter. See the [compatibility guide](https://simtlix.github.io/simfinity.js/compatibility.html) for backend-specific behavior.