US7.2: Add-a-New-Stack Tutorial

[Nachitrix]

As a new developer,
I want a step-by-step guide on how to add a "Svelte + Go + PostgreSQL" stack,
So that I can replicate the process for any future stack.

Acceptance Criteria:

• Markdown file docs/adding_new_stack.md contains:
  1. Copy-and-paste instructions for AINative template definitions (svelte-component, go-route, gorm-model).
  2. How to edit app_generation_plan.txt to detect tech_stack == "Svelte + Go + PostgreSQL".
  3. How to add new <option> to the frontend form for the new stack.
  4. Example "sample spec" JSON:

     {
       "project_name": "SvelteNotes",
       "description": "A Svelte + Go notes app",
       "features": ["User login", "Note CRUD"],
       "tech_stack": "Svelte + Go + PostgreSQL",
       "styling": "TailwindCSS",
       "canvasLayout": []
     }

  5. Expected JSON plan returned by Ollama.
• Following the tutorial end-to-end yields a minimal generated project with frontend/src/*.svelte and backend/main.go.