feat: add log db (#10086)

Add a log DB. The goal is just to store our logs in a `.sqlite` DB to
make it easier to crawl them and drop the oldest ones.

codex-rs/state/src/model/mod.rs

@@ -0,0 +1,15 @@
+mod log;
+mod thread_metadata;
+
+pub use log::LogEntry;
+pub use thread_metadata::Anchor;
+pub use thread_metadata::BackfillStats;
+pub use thread_metadata::ExtractionOutcome;
+pub use thread_metadata::SortKey;
+pub use thread_metadata::ThreadMetadata;
+pub use thread_metadata::ThreadMetadataBuilder;
+pub use thread_metadata::ThreadsPage;
+
+pub(crate) use thread_metadata::ThreadRow;
+pub(crate) use thread_metadata::anchor_from_item;
+pub(crate) use thread_metadata::datetime_to_epoch_seconds;