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/src/driver/redis/mod.rs

@@ -0,0 +1,14 @@
+mod client;
+mod kv;
+mod lock;
+mod namespace;
+mod stream;
+
+pub use client::{RedisClient, RedisClientConfig, RedisClientFactory};
+pub use kv::{RedisKvRunner, RedisKvRunnerConfig};
+pub use lock::{RedisLockKey, RedisLockLease, RedisLockRunner, RedisLockRunnerConfig};
+pub use namespace::RedisKeyspace;
+pub use stream::{
+    RedisConsumerGroup, RedisConsumerName, RedisStreamEntry, RedisStreamName,
+    RedisStreamReclaimConfig, RedisStreamReclaimResult, RedisStreamRunner, RedisStreamRunnerConfig,
+};