docs: add CONTRIBUTING.md with setup, code style, and PR guide

CONTRIBUTING.md

@@ -0,0 +1,199 @@
+# Contributing to Video Translator
+
+Thank you for your interest in contributing! This guide covers everything you need to get started.
+
+## Table of Contents
+- [Prerequisites](#prerequisites)
+- [Local Setup](#local-setup)
+- [Code Style](#code-style)
+- [Pre-commit Hooks](#pre-commit-hooks)
+- [Submitting a Pull Request](#submitting-a-pull-request)
+- [Reporting Bugs](#reporting-bugs)
+- [Project Structure](#project-structure)
+
+---
+
+## Prerequisites
+
+- Python **3.10+**
+- [Frappe Bench](https://frappeframework.com/docs/user/en/installation) installed and configured
+- A running Frappe site (v15+)
+- RabbitMQ (for background queue processing)
+
+---
+
+## Local Setup
+
+```bash
+# 1. Get the app into your bench
+cd $PATH_TO_YOUR_BENCH
+bench get-app git@github.com:theapprenticeproject/Video_Translation.git --branch main
+bench install-app my_app
+
+# 2. Create the required folders under your site's public directory
+mkdir -p sites/<your_site_name>/public/files/original
+mkdir -p sites/<your_site_name>/public/files/processed
+
+# 3. Install Python dev dependencies (uses uv)
+pip install uv
+uv sync
+
+# 4. Start bench
+bench start
+```
+
+> **Note:** The `original/` and `processed/` folders must be created manually before
+> first use. Uploads will fail with a `FileNotFoundError` if they don't exist.
+
+---
+
+## Code Style
+
+### Python
+This project uses **[Ruff](https://docs.astral.sh/ruff/)** for linting and formatting.
+
+```bash
+# Check for lint issues
+ruff check .
+
+# Auto-fix lint issues
+ruff check . --fix
+
+# Format code
+ruff format .
+```
+
+Key style rules (from `pyproject.toml`):
+- Line length: **110 characters**
+- Target: **Python 3.10**
+- Indentation: **tabs** (not spaces)
+- Quote style: **double quotes**
+
+### Commit Messages
+This project follows **[Conventional Commits](https://www.conventionalcommits.org/)**.
+
+Format: `<type>(<scope>): <short description>`
+
+| Type | When to use |
+|---|---|
+| `feat` | New feature |
+| `fix` | Bug fix |
+| `docs` | Documentation only |
+| `refactor` | Code change that neither fixes a bug nor adds a feature |
+| `test` | Adding or updating tests |
+| `chore` | Build process, dependency updates, etc. |
+| `perf` | Performance improvement |
+
+Examples:
+```
+feat(api): add batch video upload endpoint
+fix(file-naming): sync Frappe File record after physical move
+docs(readme): clarify folder setup requirement
+```
+
+---
+
+## Pre-commit Hooks
+
+Install pre-commit to catch issues before they reach CI:
+
+```bash
+pip install pre-commit
+pre-commit install
+```
+
+The hooks run Ruff on every commit. If Ruff fails, the commit is blocked until you fix the issues.
+
+To run hooks manually on all files:
+```bash
+pre-commit run --all-files
+```
+
+---
+
+## Submitting a Pull Request
+
+1. **Fork** the repository and create a branch:
+   ```bash
+   git checkout -b fix/your-fix-name
+   # or
+   git checkout -b feat/your-feature-name
+   ```
+
+2. **Make your changes.** Keep PRs focused — one logical change per PR.
+
+3. **Run the linter** before committing:
+   ```bash
+   ruff check . && ruff format --check .
+   ```
+
+4. **Commit** using conventional commit format:
+   ```bash
+   git commit -m "fix(scope): short description of what changed"
+   ```
+
+5. **Push** and open a Pull Request against the `main` branch.
+
+6. **Reference the issue** in your PR description:
+   ```
+   Fixes #<issue-number>
+   ```
+
+### PR Description Template
+```markdown
+## What
+One sentence: what this PR does.
+
+## Why
+What problem it solves. Link to the issue: Fixes #X
+
+## Changes
+- `file_naming.py`: description of change
+- `video_info.py`: description of change
+
+## Testing
+Steps to verify the fix or feature works as expected.
+```
+
+---
+
+## Reporting Bugs
+
+Open an issue on GitHub with:
+1. A clear title describing the problem
+2. Steps to reproduce
+3. Expected behaviour vs actual behaviour
+4. Relevant logs (from `bench logs` or the Frappe error log)
+5. Environment: Frappe version, Python version, OS
+
+---
+
+## Project Structure
+
+```
+Video_Translation/
+├── my_app/
+│   ├── api/
+│   │   ├── v1/                 ← V1 API endpoints (Bhashini, audio extraction, subtitles)
+│   │   └── v2/                 ← V2 API endpoints (segment tasks, ElevenLabs, onscreen text)
+│   ├── helper/
+│   │   ├── file_naming.py      ← File move + rename logic after upload
+│   │   ├── videolink_download.py ← HTTP video URL download helper
+│   │   └── options.py          ← Language/config constants
+│   ├── media-queues/
+│   │   └── tasks_pipe.py       ← RabbitMQ consumer — processes translation jobs
+│   └── self_app/
+│       └── doctype/
+│           └── video_info/     ← Core Frappe DocType (upload, move, track video)
+├── pyproject.toml              ← Project config + Ruff settings
+└── README.md
+```
+
+### Key Concepts
+
+- **VideoInfo DocType**: the central record for each uploaded video. `on_update` moves the file
+  into `files/original/` and triggers downstream processing via RabbitMQ.
+- **file_retitling()**: renames and moves uploaded files. Always updates the Frappe `File` record
+  after moving to prevent orphaned references (see issue #4).
+- **V1 vs V2 APIs**: V1 uses Bhashini for translation; V2 uses ElevenLabs + segment-based processing.
+  Both pipelines write results to `files/processed/`.