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/lib/api/usage.ts

@@ -9,6 +9,8 @@ import type {
   ModelPricing,
   ProviderLimitStatus,
   PaginatedLogs,
+  SessionSyncResult,
+  DataSourceSummary,
 } from "@/types/usage";
 import type { UsageResult } from "@/types";
 import type { AppId } from "./types";
@@ -115,4 +117,13 @@ export const usageApi = {
   ): Promise<ProviderLimitStatus> => {
     return invoke("check_provider_limits", { providerId, appType });
   },
+
+  // Session usage sync
+  syncSessionUsage: async (): Promise<SessionSyncResult> => {
+    return invoke("sync_session_usage");
+  },
+
+  getDataSourceBreakdown: async (): Promise<DataSourceSummary[]> => {
+    return invoke("get_usage_data_sources");
+  },
 };