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

app/db.py

@@ -193,10 +193,10 @@ def init_db():
                 prop_type TEXT NOT NULL DEFAULT 'text',
                 options_json TEXT DEFAULT '[]',
                 number_format TEXT DEFAULT 'number',
-                related_collection_id INTEGER REFERENCES collections(id),
+                related_collection_id INTEGER REFERENCES collections(id) ON DELETE SET NULL,
                 reverse_name TEXT,
-                relation_property_id INTEGER REFERENCES collection_properties(id),
-                target_property_id INTEGER REFERENCES collection_properties(id),
+                relation_property_id INTEGER REFERENCES collection_properties(id) ON DELETE SET NULL,
+                target_property_id INTEGER REFERENCES collection_properties(id) ON DELETE SET NULL,
                 rollup_function TEXT,
                 formula_expression TEXT,
                 position INTEGER NOT NULL DEFAULT 0,