feat(wfe-sqlite): add SQLite persistence provider

SqlitePersistenceProvider using sqlx with in-memory and file-based
SQLite. Schema with 6 tables, 8 indexes, created via ensure_store_exists.
Transactions for multi-table operations. Passes persistence_suite tests.

wfe-sqlite/Cargo.toml

@@ -0,0 +1,24 @@
+[package]
+name = "wfe-sqlite"
+version.workspace = true
+edition.workspace = true
+license.workspace = true
+description = "SQLite persistence provider for WFE"
+
+[dependencies]
+wfe-core = { workspace = true }
+sqlx = { workspace = true }
+tokio = { workspace = true }
+serde = { workspace = true }
+serde_json = { workspace = true }
+async-trait = { workspace = true }
+uuid = { workspace = true }
+chrono = { workspace = true }
+thiserror = { workspace = true }
+tracing = { workspace = true }
+
+[dev-dependencies]
+wfe-core = { workspace = true, features = ["test-support"] }
+pretty_assertions = { workspace = true }
+rstest = { workspace = true }
+tokio = { workspace = true, features = ["test-util"] }