feat(v1.5.0): Relations, Rollups, Formulas — FormulaEngine, RollupEngine, API

- FormulaEngine: 19 functions (prop, if, concat, round, now, today, dateAdd, replace, ...)
- RollupEngine: 12 aggregations (count, sum, avg, min, max, range, unique, percent_checked)
- API relation: POST /db/{id}/properties/relation + /link (bidirectional)
- API rollup: POST /db/rollup/compute
- API formula: POST /db/formula/evaluate
- FKs fix: related_collection_id/relation_property_id/target_property_id → ON DELETE SET NULL
- 43/43 tests passent (+5 tests v1.5)
- Version 1.4.0 → 1.5.0
- Docs: ROADMAP, CHANGELOG à jour

CHANGELOG.md

@@ -1,5 +1,22 @@
 # Changelog — FlowDeck
 
+## v1.5.0 (2026-07-10) — Relations & Rollups
+
+### Added
+- **Type `relation`**: lien bidirectionnel entre collections avec reverse_name auto
+  - API: `POST /db/{id}/properties/relation`, `POST /db/{id}/properties/relation/link`
+- **FormulaEngine**: 19 fonctions (prop, if, concat, round, now, today, dateAdd, replace, ...)
+  - API: `POST /db/formula/evaluate`
+- **RollupEngine**: 12 fonctions (count, sum, avg, min, max, range, unique, percent_checked, ...)
+  - API: `POST /db/rollup/compute`
+- **Tests**: 5 nouveaux tests (43/43 passent, +13%)
+
+### Fixed
+- FKs `related_collection_id`, `relation_property_id`, `target_property_id` → `ON DELETE SET NULL`
+
+### Changed
+- Version 1.4.0 → 1.5.0
+
 ## v1.4.0 (2026-07-10) — Propriétés Avancées
 
 ### Added