Feat: Backend scaffolding and local dev stack

Documentation/CONTRIBUTING

@@ -9,8 +9,8 @@ This project is still in an early scaffold stage, so the goal is to keep changes
 ### Project structure
 
 - `Frontend/` — SolidStart frontend workspace
-- `Backend/` — backend placeholder
-- `Proxy/` — proxy placeholder
+- `Backend/` — Go backend services (`web`, `api`, `worker`)
+- `Proxy/` — local production proxy/runtime assets
 - `Docker/` — local Docker Compose files
 - `Env/` — local environment files
 - `Commands/` — Just command modules and entrypoints
@@ -39,7 +39,8 @@ Main local development flow:
 just local dev
 ```
 
-This command builds the frontend development image and starts the local development stack.
+This command builds the frontend and backend development images, then starts the
+local development stack for Postgres, Valkey, frontend, and backend services.
 
 ### Local environment
 
@@ -49,7 +50,16 @@ Local development uses:
 Env/.env.local
 ```
 
-If local environment values are missing, create or update that file before starting the stack.
+The template lives at:
+
+```bash
+Env/.env.example
+```
+
+When you start the local Docker stack, the dev scripts will create `Env/.env.local`
+from `Env/.env.example` automatically if it does not already exist.
+
+If you need custom local values, edit `Env/.env.local` after it is created.
 
 ## Commit Naming Convention