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

specs/003-project-launch-script/research.md

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+# Research: Project Launch Script
+
+## Decision: Bash Script with `trap` and Background Processes
+
+### Rationale
+A bash script is the most portable and lightweight way to meet the requirement of a single command (`./run.sh`) without introducing additional process management dependencies like `pm2` or `concurrently` (unless we want to use `npm` to run everything, but the user asked for a script).
+
+### Alternatives Considered
+1.  **`concurrently` (NPM package)**:
+    - *Pros*: Easy to use, handles output well.
+    - *Cons*: Requires `npm install` before it can even run. The goal is a script that *handles* the install.
+2.  **`docker-compose`**:
+    - *Pros*: Perfect for multi-service orchestration.
+    - *Cons*: Overkill for a simple local dev environment; requires Docker to be installed and configured.
+3.  **Python script**:
+    - *Pros*: Better cross-platform support (Windows/Linux).
+    - *Cons*: Slightly more verbose for process management than bash on Linux.
+
+## Technical Findings
+
+### 1. Concurrent Execution & Graceful Shutdown
+To run processes concurrently and handle Ctrl+C:
+```bash
+#!/bin/bash
+
+# Cleanup function
+cleanup() {
+    echo "Stopping services..."
+    kill $BACKEND_PID $FRONTEND_PID
+    exit
+}
+
+# Trap SIGINT (Ctrl+C)
+trap cleanup SIGINT
+
+# Start Backend
+cd backend && python3 -m uvicorn src.app:app --reload --port 8000 &
+BACKEND_PID=$!
+
+# Start Frontend
+cd frontend && npm run dev -- --port 5173 &
+FRONTEND_PID=$!
+
+# Wait for processes
+wait
+```
+
+### 2. Dependency Checking
+- **Backend**: Check for `venv`. If missing, create it and install requirements.
+- **Frontend**: Check for `frontend/node_modules`. If missing, run `npm install`.
+
+### 3. Environment Validation
+- Check `command -v python3` and `command -v npm`.
+
+## Best Practices
+- Use colors for logs to distinguish between Backend and Frontend output.
+- Use `set -e` to exit on error during setup, but disable it or handle it carefully when starting background processes.