fix: remove stale deals.csv references, add extract+store to launch_backtest

- FilePaths struct: remove deals_csv/deals_json fields (deals go to DB only)
- save_metadata: stop writing stale CSV/JSON paths to pipeline_metadata.json
- get_backtest_status: remove deals.csv artifact check (was unused in logic)
- get_backtest_crash_info: check DB deal count and metrics.json instead of deals.csv
- export_report: remove unused _deals_path variable
- launch_backtest: monitor_backtest_completion now calls extract_and_store when
  report found — extracts metrics+deals, registers report in DB, deletes htm file

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/models/report.rs

@@ -14,8 +14,6 @@ pub struct Report {
     pub from_date: String,
     pub to_date: String,
     pub metrics_file: PathBuf,
-    pub deals_csv: PathBuf,
-    pub deals_json: PathBuf,
     pub analysis_file: Option<PathBuf>,
 }
 
@@ -42,8 +40,6 @@ pub struct PipelineMetadata {
 pub struct FilePaths {
     pub metrics: String,
     pub analysis: String,
-    pub deals_csv: String,
-    pub deals_json: String,
 }
 
 #[allow(dead_code)]