Document pgbackweb database settings

Hey— Thanks for pgbackweb! I have just successfully set it up and backed up a database to Cloudflare R2. There were two things that were a bit confusing while setting it up. Just sharing it here in case others stumble upon them. **Database settings** I ran into the problem where it tried to use extensions outside of the search path, so the following worked for me. I think it would be helpful to document the settings needed for the goose migrations to run successfully. As my postgres user: ``` CREATE USER pgbackwebdb WITH CREATEDB PASSWORD 'redacted'; CREATE DATABASE pgbackwebdb; CREATE EXTENSION IF NOT EXISTS pgcrypto WITH SCHEMA public; CREATE EXTENSION IF NOT EXISTS "uuid-ossp" WITH SCHEMA public; ``` In the `pgbackwebdb` database: ``` CREATE schema pgbackwebdb; ALTER ROLE pgbackwebdb SET search_path = pgbackwebdb, public; GRANT USAGE ON SCHEMA pgbackwebdb TO pgbackwebdb; GRANT CREATE ON SCHEMA pgbackwebdb TO pgbackwebdb; ALTER DATABASE pgbackwebdb OWNER TO pgbackwebdb; GRANT CREATE ON DATABASE pgbackwebdb TO pgbackwebdb; ``` **Cloudflare R2** The following issue was helpful (https://github.com/eduardolat/pgbackweb/issues/117), maybe having a dropdown to select which S3 provider one is using would be nice. <img width="1312" height="1046" alt="Image" src="https://github.com/user-attachments/assets/1efa980b-a9e5-4369-a822-4c29658d8a54" /> Thanks!