fix: remove teams foreign key constraint from UserFact

- Remove FK constraint from UserFact.team_id (teams table may not exist)
- Update SQL migration to remove FK constraint
- team_id remains optional String field without FK

services/memory-service/migrations/001_create_memory_tables.sql

@@ -9,7 +9,7 @@ CREATE EXTENSION IF NOT EXISTS "vector";
 CREATE TABLE IF NOT EXISTS user_facts (
     id UUID PRIMARY KEY DEFAULT gen_random_uuid(),
     user_id TEXT NOT NULL REFERENCES users(id) ON DELETE CASCADE,
-    team_id TEXT REFERENCES teams(id) ON DELETE CASCADE,
+    team_id TEXT,  -- Без FK constraint, оскільки teams може не існувати
     
     -- Ключ факту (наприклад: "language", "is_donor", "is_validator", "top_contributor")
     fact_key TEXT NOT NULL,