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

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

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+# Implementation Plan: Project Launch Script
+
+**Branch**: `003-project-launch-script` | **Date**: 2025-12-20 | **Spec**: [specs/003-project-launch-script/spec.md](specs/003-project-launch-script/spec.md)
+**Input**: Feature specification from `/specs/003-project-launch-script/spec.md`
+
+## Summary
+
+Create a root-level bash script (`run.sh`) to automate the setup and concurrent execution of the backend (FastAPI) and frontend (Svelte/Vite) development servers. The script will handle dependency checks, installation, and graceful termination of both processes.
+
+## Technical Context
+
+**Language/Version**: Python 3.9+, Node.js 18+  
+**Primary Dependencies**: `uvicorn`, `npm`, `bash`  
+**Storage**: N/A  
+**Testing**: Manual verification of service availability; `pytest` for backend logic if any.  
+**Target Platform**: Linux  
+**Project Type**: Web application (frontend + backend)  
+**Performance Goals**: Services accessible within 30 seconds.  
+**Constraints**: Must handle `SIGINT` (Ctrl+C) to kill all child processes.  
+**Scale/Scope**: Developer utility script.
+
+## Constitution Check
+
+*GATE: Must pass before Phase 0 research. Re-check after Phase 1 design.*
+
+| Gate | Status | Rationale |
+|------|--------|-----------|
+| Python 3.9+ | PASS | Backend uses Python 3.9+ |
+| Node.js 18+ | PASS | Frontend uses Node.js 18+ |
+| Project Structure | PASS | Follows `backend/`, `frontend/` structure |
+| Executable from root | PASS | Planned as `./run.sh` |
+
+**Post-Design Re-evaluation**: Design artifacts (research, data-model, contracts) confirm compliance with all project principles. No violations found.
+
+## Project Structure
+
+### Documentation (this feature)
+
+```text
+specs/003-project-launch-script/
+├── plan.md              # This file
+├── research.md          # Phase 0 output
+├── data-model.md        # Phase 1 output
+├── quickstart.md        # Phase 1 output
+├── contracts/           # Phase 1 output
+└── tasks.md             # Phase 2 output
+```
+
+### Source Code (repository root)
+
+```text
+run.sh                   # New launch script
+
+backend/
+├── src/
+│   └── app.py
+└── requirements.txt
+
+frontend/
+├── src/
+└── package.json
+```
+
+**Structure Decision**: Option 2: Web application. The script will reside in the root to orchestrate both directories.
+
+## Complexity Tracking
+
+> **Fill ONLY if Constitution Check has violations that must be justified**
+
+| Violation | Why Needed | Simpler Alternative Rejected Because |
+|-----------|------------|-------------------------------------|
+| None | - | - |