Set database URIs in CI to bypass Docker fallback

The test infrastructure checks if Docker is available before trying
native databases. Since GitHub Actions runners have Docker installed,
tests were trying to start MySQL/PostgreSQL via Docker instead of using
the databases already started by sqlc-test-setup.

Setting POSTGRESQL_SERVER_URI and MYSQL_SERVER_URI explicitly ensures
tests connect to the native databases.

https://claude.ai/code/session_01CsyRwSkRxBcQoaQFVkMQsJ

Author: claude

.github/workflows/ci.yml

@@ -62,6 +62,8 @@ jobs:
         CI_SQLC_PROJECT_ID: ${{ secrets.CI_SQLC_PROJECT_ID }}
         CI_SQLC_AUTH_TOKEN: ${{ secrets.CI_SQLC_AUTH_TOKEN }}
         SQLC_AUTH_TOKEN: ${{ secrets.CI_SQLC_AUTH_TOKEN }}
+        POSTGRESQL_SERVER_URI: "postgres://postgres:postgres@127.0.0.1:5432/postgres?sslmode=disable"
+        MYSQL_SERVER_URI: "root:mysecretpassword@tcp(127.0.0.1:3306)/mysql?multiStatements=true&parseTime=true"
         CGO_ENABLED: "0"
 
   vuln_check: