Add README documentation for OpenAPI generator (#45)

* Add README documentation for OpenAPI generator

Document the OpenAPI client generation tooling including usage instructions,
directory structure, configuration options, and troubleshooting tips.

* Apply suggestion from @Copilot

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Claude <noreply@anthropic.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

openapi/README.md

@@ -0,0 +1,124 @@
+# OpenAPI Generator
+
+This directory contains the tooling to generate a TypeScript Axios client from the FastAPI backend's OpenAPI specification.
+
+## Overview
+
+The generator performs two main tasks:
+
+1. **Extract OpenAPI Schema** - Imports the FastAPI application and generates the OpenAPI JSON specification
+2. **Generate TypeScript Client** - Uses OpenAPI Generator CLI (via Docker) to create a typed Axios client
+
+## Prerequisites
+
+- **Python 3.x** with the backend dependencies installed
+- **Docker** - Required to run the OpenAPI Generator CLI
+
+## Directory Structure
+
+```
+openapi/
+├── README.md                 # This file
+├── generate.py               # Main generator script
+├── openapi.json              # Generated OpenAPI specification
+└── templates/
+    └── typescript-axios/
+        └── baseApi.mustache  # Custom template for base API configuration
+```
+
+## Usage
+
+Run the generator from the project root:
+
+```bash
+cd /path/to/inquiro
+python openapi/generate.py
+```
+
+This will:
+
+1. Load environment variables from `backend/dev.env`
+2. Import the FastAPI app from `app.main`
+3. Generate `openapi/openapi.json` from the app's routes
+4. Run the OpenAPI Generator CLI via Docker
+5. Output the TypeScript Axios client to `frontend/src/api/`
+
+## Generated Output
+
+The generator creates the following structure in `frontend/src/api/`:
+
+```
+frontend/src/api/
+├── api.ts              # Aggregated API exports
+├── base.ts             # Base API class with Axios configuration
+├── common.ts           # Common utilities
+├── configuration.ts    # API configuration options
+├── index.ts            # Main entry point
+├── apis/               # Generated API classes by tag
+│   ├── authentication-api.ts
+│   ├── users-api.ts
+│   ├── projects-api.ts
+│   ├── paper-api.ts
+│   └── search-api.ts
+└── models/             # TypeScript interfaces for request/response types
+    ├── index.ts
+    ├── user-create.ts
+    ├── user-response.ts
+    └── ...
+```
+
+## Configuration
+
+The generator uses these settings in `generate.py`:
+
+| Variable | Description |
+|----------|-------------|
+| `BACKEND_APP_IMPORT` | Python module path to FastAPI app (`app.main`) |
+| `OUTPUT_SCHEMA` | Path for generated OpenAPI JSON |
+| `CLIENT_OUTPUT_DIR` | Output directory for TypeScript client |
+
+### OpenAPI Generator Options
+
+The Docker command includes these options:
+
+- `-g typescript-axios` - Generate TypeScript client using Axios
+- `-t /local/openapi/templates/typescript-axios` - Use custom templates
+- `--skip-validate-spec` - Skip OpenAPI spec validation
+- `supportsES6=true` - Generate ES6 compatible code
+- `withSeparateModelsAndApi=true` - Separate models and API files
+- `apiPackage=apis` - Place API files in `apis/` subdirectory
+- `modelPackage=models` - Place model files in `models/` subdirectory
+- `--global-property=apiDocs=false,modelDocs=false,apiTests=false,modelTests=false` - Disable generation of API docs, model docs, and test files
+
+## Custom Templates
+
+The `templates/typescript-axios/baseApi.mustache` template customizes the base API class to:
+
+- Use Vite's environment variable `VITE_API_BASE_URL` for the API base path
+- Configure the default Axios instance
+
+## Environment Variables
+
+The generated client expects the following environment variable in the frontend:
+
+```env
+VITE_API_BASE_URL=http://localhost:8000
+```
+
+## Troubleshooting
+
+### Docker Permission Issues
+
+If you encounter Docker permission errors, ensure your user is in the `docker` group:
+
+```bash
+sudo usermod -aG docker $USER
+```
+
+### Module Import Errors
+
+If the FastAPI app fails to import, ensure:
+
+1. You're running from the project root directory
+2. Backend dependencies are installed (`pip install -r backend/requirements.txt`)
+3. The `backend/dev.env` file exists with required environment variables