update to support postgresql and add godocs

README.md

@@ -114,6 +114,25 @@ Create a new up/down migration file with this command
 goose -dir db/migrations sqlite3 ./db.sqlite3 create init sql
 ```
 
+#### Database Configuration
+By default the app uses SQLite and creates/opens `db.sqlite3`. You can opt into PostgreSQL
+by setting environment variables:
+
+- `DB_DRIVER`: `sqlite` (default) or `postgres`
+- `DB_URL`: SQLite file path/DSN or PostgreSQL DSN
+
+Examples:
+```shell
+# SQLite (default)
+DB_DRIVER=sqlite DB_URL=./db.sqlite3
+
+# PostgreSQL
+DB_DRIVER=postgres DB_URL=postgres://user:pass@localhost:5432/vctp?sslmode=disable
+```
+
+PostgreSQL migrations live in `db/migrations_postgres`, while SQLite migrations remain in
+`db/migrations`.
+
 ### Dist
 
 This is where your assets live. Any Javascript, images, or styling needs to go in the