Add multi-database data layer

Introduce aether-data-schema and driver-specific schema generation for Postgres, MySQL, and SQLite.

Split data backends, lifecycle, repositories, and gateway runtime integration across database drivers.

Verified with cargo fmt --all --check, cargo clippy --workspace --all-targets -- -D warnings, and cargo test --workspace.

crates/aether-data-contracts/src/repository/usage/mod.rs

@@ -1,21 +1,23 @@
 mod types;
 
 pub use types::{
-    parse_usage_body_ref, usage_body_ref, StoredProviderApiKeyUsageSummary,
-    StoredProviderUsageSummary, StoredProviderUsageWindow, StoredRequestUsageAudit,
-    StoredUsageAuditAggregation, StoredUsageAuditSummary, StoredUsageBreakdownSummaryRow,
-    StoredUsageCacheAffinityHitSummary, StoredUsageCacheAffinityIntervalRow,
-    StoredUsageCacheHitSummary, StoredUsageCostSavingsSummary, StoredUsageDailySummary,
-    StoredUsageDashboardDailyBreakdownRow, StoredUsageDashboardProviderCount,
-    StoredUsageDashboardSummary, StoredUsageErrorDistributionRow, StoredUsageLeaderboardSummary,
+    parse_usage_body_ref, usage_body_ref, PendingUsageCleanupSummary,
+    StoredProviderApiKeyUsageSummary, StoredProviderUsageSummary, StoredProviderUsageWindow,
+    StoredRequestUsageAudit, StoredUsageAuditAggregation, StoredUsageAuditSummary,
+    StoredUsageBreakdownSummaryRow, StoredUsageCacheAffinityHitSummary,
+    StoredUsageCacheAffinityIntervalRow, StoredUsageCacheHitSummary, StoredUsageCostSavingsSummary,
+    StoredUsageDailySummary, StoredUsageDashboardDailyBreakdownRow,
+    StoredUsageDashboardProviderCount, StoredUsageDashboardSummary,
+    StoredUsageErrorDistributionRow, StoredUsageLeaderboardSummary,
     StoredUsagePerformancePercentilesRow, StoredUsageSettledCostSummary,
     StoredUsageTimeSeriesBucket, StoredUsageUserTotals, UpsertUsageRecord,
     UsageAuditAggregationGroupBy, UsageAuditAggregationQuery, UsageAuditKeywordSearchQuery,
     UsageAuditListQuery, UsageAuditSummaryQuery, UsageBodyCaptureResult, UsageBodyCaptureState,
     UsageBodyCaptureStorage, UsageBodyField, UsageBreakdownGroupBy, UsageBreakdownSummaryQuery,
     UsageCacheAffinityHitSummaryQuery, UsageCacheAffinityIntervalGroupBy,
-    UsageCacheAffinityIntervalQuery, UsageCacheHitSummaryQuery, UsageCostSavingsSummaryQuery,
-    UsageDailyHeatmapQuery, UsageDashboardDailyBreakdownQuery, UsageDashboardProviderCountsQuery,
+    UsageCacheAffinityIntervalQuery, UsageCacheHitSummaryQuery, UsageCleanupSummary,
+    UsageCleanupWindow, UsageCostSavingsSummaryQuery, UsageDailyHeatmapQuery,
+    UsageDashboardDailyBreakdownQuery, UsageDashboardProviderCountsQuery,
     UsageDashboardSummaryQuery, UsageErrorDistributionQuery, UsageLeaderboardGroupBy,
     UsageLeaderboardQuery, UsageMonitoringErrorCountQuery, UsageMonitoringErrorListQuery,
     UsagePerformancePercentilesQuery, UsageReadRepository, UsageRepository,

crates/aether-data-contracts/src/repository/usage/types.rs

@@ -1,4 +1,5 @@
 use async_trait::async_trait;
+use chrono::{DateTime, Utc};
 use serde_json::Value;
 
 /// Joined usage read model assembled from the accounting row plus the newer audit/snapshot
@@ -1568,12 +1569,57 @@ pub trait UsageWriteRepository: Send + Sync {
     async fn rebuild_api_key_usage_stats(&self) -> Result<u64, crate::DataLayerError>;
 
     async fn rebuild_provider_api_key_usage_stats(&self) -> Result<u64, crate::DataLayerError>;
+
+    async fn cleanup_stale_pending_requests(
+        &self,
+        cutoff_unix_secs: u64,
+        now_unix_secs: u64,
+        timeout_minutes: u64,
+        batch_size: usize,
+    ) -> Result<PendingUsageCleanupSummary, crate::DataLayerError> {
+        let _ = (cutoff_unix_secs, now_unix_secs, timeout_minutes, batch_size);
+        Ok(PendingUsageCleanupSummary::default())
+    }
+
+    async fn cleanup_usage(
+        &self,
+        window: &UsageCleanupWindow,
+        batch_size: usize,
+        auto_delete_expired_keys: bool,
+    ) -> Result<UsageCleanupSummary, crate::DataLayerError> {
+        let _ = (window, batch_size, auto_delete_expired_keys);
+        Ok(UsageCleanupSummary::default())
+    }
 }
 
 pub trait UsageRepository: UsageReadRepository + UsageWriteRepository + Send + Sync {}
 
 impl<T> UsageRepository for T where T: UsageReadRepository + UsageWriteRepository + Send + Sync {}
 
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default)]
+pub struct PendingUsageCleanupSummary {
+    pub failed: usize,
+    pub recovered: usize,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Default, serde::Serialize, serde::Deserialize)]
+pub struct UsageCleanupSummary {
+    pub body_externalized: usize,
+    pub legacy_body_refs_migrated: usize,
+    pub body_cleaned: usize,
+    pub header_cleaned: usize,
+    pub keys_cleaned: usize,
+    pub records_deleted: usize,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq, serde::Serialize, serde::Deserialize)]
+pub struct UsageCleanupWindow {
+    pub detail_cutoff: DateTime<Utc>,
+    pub compressed_cutoff: DateTime<Utc>,
+    pub header_cutoff: DateTime<Utc>,
+    pub log_cutoff: DateTime<Utc>,
+}
+
 fn parse_u64(value: i32, field_name: &str) -> Result<u64, crate::DataLayerError> {
     u64::try_from(value).map_err(|_| {
         crate::DataLayerError::UnexpectedValue(format!("invalid {field_name}: {value}"))