Move psycopg2-binary to be a default dep

The Python buildpack runs `uv sync --locked --no-default-groups` which
excludes psychopg2-binary, which crashes Django.

Author: strugee

pyproject.toml

@@ -62,6 +62,7 @@ dependencies = [
   "urlman~=2.0.1",
   "vobject~=0.9.0",
   "whitenoise[brotli]~=6.12.0",
+  "psycopg2-binary~=2.9.0",
 ]
 
 [project.optional-dependencies]
@@ -95,7 +96,6 @@ devdocs = [
   "sphinxcontrib-httpdomain",
   "sphinxcontrib-spelling",
 ]
-postgres = ["psycopg2-binary~=2.9.0"]
 
 [build-system]
 build-backend = "backend"