Remove leftover psql references (#541)

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## Motivation and Context
<!-- Why is this change needed? What problem does it solve? -->
Housekeeping on leftover psql references

## How Has This Been Tested?
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tested? -->

## Breaking Changes
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## Types of changes
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the boxes that apply: -->
- [ ] Bug fix (non-breaking change which fixes an issue)
- [ ] New feature (non-breaking change which adds functionality)
- [ ] Breaking change (fix or feature that would cause existing
functionality to change)
- [ ] Documentation update

## Checklist
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that apply. -->
- [ ] I have read the [MCP
Documentation](https://modelcontextprotocol.io)
- [ ] My code follows the repository's style guidelines
- [ ] New and existing tests pass locally
- [ ] I have added appropriate error handling
- [ ] I have added or updated documentation as needed

## Additional context
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Signed-off-by: Radoslav Dimitrov <radoslav@stacklok.com>

.env.example

@@ -5,8 +5,6 @@ MCP_REGISTRY_SERVER_ADDRESS=:8080
 MCP_REGISTRY_VERSION=dev
 
 # Database configuration
-# Supported types: postgresql
-MCP_REGISTRY_DATABASE_TYPE=postgresql
 MCP_REGISTRY_DATABASE_URL=postgres://username:password@localhost:5432/mcp-registry
 
 # Path or URL to import seed data (supports local files and HTTP URLs)

internal/config/config.go

@@ -4,17 +4,10 @@ import (
 	env "github.com/caarlos0/env/v11"
 )
 
-type DatabaseType string
-
-const (
-	DatabaseTypePostgreSQL DatabaseType = "postgresql"
-)
-
 // Config holds the application configuration
 // See .env.example for more documentation
 type Config struct {
 	ServerAddress            string       `env:"SERVER_ADDRESS" envDefault:":8080"`
-	DatabaseType             DatabaseType `env:"DATABASE_TYPE" envDefault:"postgresql"`
 	DatabaseURL              string       `env:"DATABASE_URL" envDefault:"postgres://localhost:5432/mcp-registry?sslmode=disable"`
 	SeedFrom                 string       `env:"SEED_FROM" envDefault:""`
 	Version                  string       `env:"VERSION" envDefault:"dev"`

tests/integration/run.sh

@@ -2,8 +2,6 @@
 
 set -e
 
-# No persistent state with ephemeral database
-
 cleanup() {
     echo "========== registry logs =========="
     docker logs registry || true