refactor(coordinator): standardize database path to follow blockchain-node pattern

- Change coordinator database from /opt/data/coordinator.db to ./data/coordinator.db
- Update config.py to use relative path consistent with blockchain-node
- Update deployment scripts to use /opt/coordinator-api/data/coordinator.db
- Add data directory creation in init_db() for consistency
- Update .env.example files to reflect new standard
- Maintain backward compatibility for production deployment

apps/coordinator-api/src/app/config.py

@@ -25,9 +25,9 @@ class DatabaseConfig(BaseSettings):
         if self.url:
             return self.url
 
-        # Default SQLite path
+        # Default SQLite path - consistent with blockchain-node pattern
         if self.adapter == "sqlite":
-            return "sqlite:////opt/data/coordinator.db"
+            return "sqlite:///./data/coordinator.db"
 
         # Default PostgreSQL connection string
         return f"{self.adapter}://localhost:5432/coordinator"
@@ -117,8 +117,8 @@ class Settings(BaseSettings):
             return self.test_database_url
         if self.database.url:
             return self.database.url
-        # Default SQLite path for backward compatibility
-        return "sqlite:////opt/data/coordinator.db"
+        # Default SQLite path - consistent with blockchain-node pattern
+        return "sqlite:///./data/coordinator.db"
 
     @database_url.setter
     def database_url(self, value: str):