feat: implement project launch script run.sh and update README

specs/003-project-launch-script/data-model.md

@@ -0,0 +1,26 @@
+# Data Model: Project Launch Script
+
+## Entities
+
+N/A - This feature is a utility script and does not involve persistent data storage or complex data structures.
+
+## Process State
+
+The script manages the lifecycle of two primary processes:
+
+1.  **Backend Process**:
+    - Command: `python3 -m uvicorn src.app:app`
+    - Port: 8000 (default)
+    - Environment: Python Virtual Environment (`.venv`)
+
+2.  **Frontend Process**:
+    - Command: `npm run dev`
+    - Port: 5173 (default)
+    - Environment: Node.js / `node_modules`
+
+## Validation Rules
+
+- `python3` must be version 3.9 or higher.
+- `npm` must be available.
+- `backend/requirements.txt` must exist.
+- `frontend/package.json` must exist.