feat: add session log usage tracking without proxy

Parse Claude Code JSONL session files (~/.claude/projects/) and Codex
SQLite database (~/.codex/state_5.sqlite) to track API usage without
requiring proxy interception. This enables usage statistics for users
who don't use the proxy feature.

Key changes:
- Add session_usage.rs: incremental JSONL parser with message.id dedup
- Add session_usage_codex.rs: import thread-level token data from Codex
- Add data_source column to proxy_request_logs (proxy/session_log/codex_db)
- Add session_log_sync table for tracking parse offsets
- Background sync every 60s + manual sync via DataSourceBar UI
- Schema migration v7→v8
- i18n support for zh/en/ja

src-tauri/src/services/mod.rs

@@ -9,6 +9,8 @@ pub mod omo;
 pub mod prompt;
 pub mod provider;
 pub mod proxy;
+pub mod session_usage;
+pub mod session_usage_codex;
 pub mod skill;
 pub mod speedtest;
 pub mod stream_check;