docs: add CONTRIBUTING.md

Author: SSheppDev

CONTRIBUTING.md

@@ -0,0 +1,59 @@
+# Contributing to sfetch
+
+## Running locally for development
+
+**Prerequisites:** Docker Desktop, Node.js 20+, Salesforce CLI with an authenticated org.
+
+```bash
+git clone https://github.com/SSheppDev/SFetch.git
+cd SFetch
+cp .env.example .env
+# Edit .env — set POSTGRES_PASSWORD at minimum
+```
+
+Start Postgres only (so the API can run outside Docker during dev):
+
+```bash
+docker compose up postgres -d
+```
+
+Run the API and UI in watch mode:
+
+```bash
+npm install
+npm run dev:api   # Express API on :7743
+npm run dev:ui    # Vite dev server on :5173
+```
+
+The Vite dev server proxies `/api` requests to the Express backend, so the full app works at `http://localhost:5173`.
+
+## Project structure
+
+```
+src/api/src/
+  auth/         SF token reader
+  db/           Postgres pool + init SQL
+  routes/       Express route handlers
+  salesforce/   Bulk API client
+  sync/         Delta sync, reconciliation, DDL, scheduler
+
+src/ui/src/
+  components/   Shared UI components
+  pages/        One file per page
+  lib/          API client, utilities
+```
+
+## Submitting a pull request
+
+1. Fork the repo and create a branch from `main`
+2. Make your changes — keep commits focused and descriptive
+3. Open a PR with a clear description of what changed and why
+4. PRs that add features should include a note on how to test them manually
+
+## Reporting bugs
+
+Open a GitHub issue with:
+- What you expected to happen
+- What actually happened
+- Relevant logs (`docker compose logs api`)
+- Your OS and Docker version