feat(EXEC-001): add hedge strategy builder

docs/roadmap/done/EXEC-001-strategy-builder.yaml

@@ -0,0 +1,19 @@
+id: EXEC-001
+title: Strategy Builder
+status: done
+priority: P1
+effort: L
+depends_on:
+  - DATA-003
+tags:
+  - strategies
+  - hedge
+summary: The product now includes a thin hedge-page strategy builder that saves reusable custom templates and immediately compares their cost vs protection in the existing hedge charts.
+completed_notes:
+  - Updated `app/services/strategy_templates.py` to persist templates under `data/strategy_templates.json`, seed from the shipped default template catalog, and expose a fail-closed `create_custom_template(...)` builder API.
+  - Added custom-template coverage in `tests/test_strategy_templates.py` for persistence, duplicate-name rejection, and custom catalog rendering.
+  - Updated `app/pages/hedge.py` to add a product-visible `Strategy Builder` card where users can choose strategy type, strike inputs, and expiration days, then save a reusable template from the UI.
+  - Saved templates now immediately participate in the existing hedge-page cost/protection comparison flow by auto-selecting the new template and reusing the existing payoff/cost charts on `/{workspace_id}/hedge`.
+  - Saved templates are reusable beyond the hedge page because the same app-global repository-backed template catalog now feeds `/backtests` and `/event-comparison` template selectors.
+  - The current thin builder scope supports custom protective puts and equal-weight two-leg put ladders; richer template management and more advanced builder controls can be added later as follow-up work.
+  - Local Docker validation closed the loop on the exact changed route: `/health` returned OK, `tests/test_hedge_builder_playwright.py` passed against the Docker-served app, and the saved template was verified as reusable from `/{workspace_id}/backtests`.