docs: add local dev workflow and ignore local n8n mount

.gitignore

@@ -5,6 +5,7 @@
 # Bind-mounted runtime state (keep folder, ignore contents)
 /data/db/
 /data/storage/
+/data/n8n/
 
 # OS / editor
 .DS_Store

README.md

@@ -25,6 +25,40 @@ Self-hosted Supabase stack + bilingual (DE/EN) public website + lead-management
 
 ## Run
 
+### Local Dev (Windows/macOS/Linux)
+
+Use the local override so bind mounts point to this repository (for example `./data/db`, `./data/storage`, `./data/n8n`).
+
+Start local stack:
+
+```bash
+docker compose -f docker-compose.yml -f docker-compose.local.yml up -d --build
+```
+
+Stop local stack:
+
+```bash
+docker compose -f docker-compose.yml -f docker-compose.local.yml down
+```
+
+Delete local mounts and recreate from scratch:
+
+```bash
+docker compose -f docker-compose.yml -f docker-compose.local.yml down -v --remove-orphans
+rm -rf ./data/db ./data/storage ./data/n8n
+mkdir -p ./data/db ./data/storage ./data/n8n
+docker compose -f docker-compose.yml -f docker-compose.local.yml up -d --build
+```
+
+PowerShell equivalent for cleanup:
+
+```powershell
+docker compose -f docker-compose.yml -f docker-compose.local.yml down -v --remove-orphans
+Remove-Item .\data\db,.\data\storage,.\data\n8n -Recurse -Force -ErrorAction SilentlyContinue
+New-Item -ItemType Directory -Path .\data\db,.\data\storage,.\data\n8n -Force | Out-Null
+docker compose -f docker-compose.yml -f docker-compose.local.yml up -d --build
+```
+
 ### Via Portainer (recommended)
 
 1. Clone the repo onto the host: `git clone <repo> /mnt/user/appdata/mc-cars`