refactor: move supabase config to repo root, fix port and env setup

- Move supabase/ from packages/db/ to repo root for simpler CLI usage
- Use custom ports (553xx) to avoid conflicts with other local Supabase instances
- Add --env-mode=loose to turbo dev so root .env vars reach Next.js
- Remove hardcoded --port 3000 from next dev (reads PORT env var instead)
- Add .env.example with Supabase env var placeholders
- Add supabase local state dirs to .gitignore

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

supabase/config.toml

@@ -0,0 +1,43 @@
+# Supabase local development configuration
+# This file is used by `supabase start` for local development
+
+project_id = "pascal-editor"
+
+[api]
+enabled = true
+port = 55321
+schemas = ["public"]
+extra_search_path = ["public"]
+max_rows = 1000
+
+[db]
+port = 55322
+shadow_port = 55320
+major_version = 17
+
+[studio]
+enabled = true
+port = 55323
+
+[inbucket]
+enabled = true
+port = 55324
+smtp_port = 55325
+pop3_port = 55326
+
+[analytics]
+enabled = true
+port = 55328
+backend = "postgres"
+
+[auth]
+enabled = true
+site_url = "http://localhost:3000"
+additional_redirect_urls = ["http://localhost:3000"]
+jwt_expiry = 3600
+enable_signup = true
+
+[auth.email]
+enable_signup = true
+double_confirm_changes = false
+enable_confirmations = false