refactor(data): remove MySQL and SQLite support

Use PostgreSQL as the only database backend across runtime, schema tooling, installation, Compose, and CI. Update regression tests and reject removed drivers explicitly.

apps/aether-gateway/src/data/config.rs

@@ -113,10 +113,7 @@ impl GatewayDataConfig {
             return (self.clone(), None);
         };
         let total_max = database.pool.max_connections;
-        if total_max < 2
-            || configured_background_max == Some(0)
-            || is_private_sqlite_memory_database(database)
-        {
+        if total_max < 2 || configured_background_max == Some(0) {
             return (self.clone(), None);
         }
 
@@ -152,14 +149,9 @@ impl GatewayDataConfig {
     }
 }
 
-fn is_private_sqlite_memory_database(database: &aether_data::SqlDatabaseConfig) -> bool {
-    database.driver == aether_data::DatabaseDriver::Sqlite
-        && matches!(database.url.trim(), "sqlite::memory:" | "sqlite://:memory:")
-}
-
 #[cfg(test)]
 mod tests {
-    use super::GatewayDataConfig;
+    use super::{GatewayDataConfig, PostgresPoolConfig};
     use aether_data::{DatabaseDriver, SqlDatabaseConfig, SqlPoolConfig};
 
     #[test]
@@ -226,7 +218,10 @@ mod tests {
 
     #[test]
     fn runtime_pool_split_can_be_disabled_or_degrade_for_single_connection() {
-        let mut database = SqlDatabaseConfig::sqlite_default();
+        let mut database = SqlDatabaseConfig::from_postgres_config(PostgresPoolConfig {
+            database_url: "postgres://localhost/aether".to_string(),
+            ..Default::default()
+        });
         database.pool.max_connections = 1;
         let config = GatewayDataConfig::from_database_config(database);
         assert!(config
@@ -234,7 +229,10 @@ mod tests {
             .1
             .is_none());
 
-        let mut database = SqlDatabaseConfig::sqlite_default();
+        let mut database = SqlDatabaseConfig::from_postgres_config(PostgresPoolConfig {
+            database_url: "postgres://localhost/aether".to_string(),
+            ..Default::default()
+        });
         database.pool.max_connections = 8;
         let config = GatewayDataConfig::from_database_config(database);
         assert!(config
@@ -242,34 +240,4 @@ mod tests {
             .1
             .is_none());
     }
-
-    #[test]
-    fn runtime_pool_split_keeps_private_sqlite_memory_database_in_one_pool() {
-        for url in ["sqlite::memory:", "sqlite://:memory:"] {
-            let config = GatewayDataConfig::from_database_config(
-                SqlDatabaseConfig::new(
-                    DatabaseDriver::Sqlite,
-                    url,
-                    SqlPoolConfig {
-                        min_connections: 1,
-                        max_connections: 8,
-                        ..SqlPoolConfig::default()
-                    },
-                )
-                .expect("sqlite memory database config should be valid"),
-            );
-
-            let (foreground, background) = config.split_runtime_pools_with_background_max(Some(2));
-
-            assert!(background.is_none(), "private SQLite URL {url} was split");
-            assert_eq!(
-                foreground
-                    .database()
-                    .expect("foreground database")
-                    .pool
-                    .max_connections,
-                8
-            );
-        }
-    }
 }

apps/aether-gateway/src/data/state/core.rs

@@ -1116,10 +1116,7 @@ impl GatewayDataState {
 }
 
 fn database_driver_supports_usage_counter_flush(driver: Option<DatabaseDriver>) -> bool {
-    matches!(
-        driver,
-        Some(DatabaseDriver::Postgres | DatabaseDriver::Mysql | DatabaseDriver::Sqlite)
-    )
+    matches!(driver, Some(DatabaseDriver::Postgres))
 }
 
 #[cfg(test)]
@@ -1132,12 +1129,6 @@ mod usage_counter_flush_backend_tests {
         assert!(database_driver_supports_usage_counter_flush(Some(
             DatabaseDriver::Postgres
         )));
-        assert!(database_driver_supports_usage_counter_flush(Some(
-            DatabaseDriver::Mysql
-        )));
-        assert!(database_driver_supports_usage_counter_flush(Some(
-            DatabaseDriver::Sqlite
-        )));
         assert!(!database_driver_supports_usage_counter_flush(None));
     }
 }

apps/aether-gateway/src/data/tests.rs

@@ -254,40 +254,6 @@ async fn app_state_wires_gateway_data_state_from_config() {
     assert!(state.data.has_video_task_reader());
 }
 
-#[tokio::test]
-async fn app_state_prepares_sqlite_database_startup() -> Result<(), Box<dyn std::error::Error>> {
-    let mut pool = SqlPoolConfig::default();
-    pool.min_connections = 0;
-    pool.max_connections = 1;
-    let database = SqlDatabaseConfig::new(DatabaseDriver::Sqlite, "sqlite::memory:", pool)?;
-    let state =
-        AppState::new()?.with_data_config(GatewayDataConfig::from_database_config(database))?;
-
-    let pending = state
-        .prepare_database_for_startup()
-        .await?
-        .expect("sqlite database should expose migration state");
-    assert!(
-        !pending.is_empty(),
-        "fresh sqlite gateway databases should report pending migrations"
-    );
-
-    assert!(
-        state.run_database_migrations().await?,
-        "sqlite gateway database should run migrations"
-    );
-    let pending = state
-        .prepare_database_for_startup()
-        .await?
-        .expect("sqlite database should expose migration state");
-    assert!(
-        pending.is_empty(),
-        "sqlite gateway databases should be current after migrations"
-    );
-
-    Ok(())
-}
-
 #[tokio::test]
 async fn data_state_checks_user_uniqueness_through_user_reader() {
     let user = StoredUserAuthRecord::new(