docs: remove db references from README

README.md

@@ -34,7 +34,6 @@ flowchart LR
         engine_core
         steering
         tank
-        db[(PostgreSQL DB)]
     end
     subgraph engine
         engine_instance[Engine]-.-oplayer & events & scheduler
@@ -47,7 +46,6 @@ flowchart LR
         subgraph scheduling
             api[Fetch & Cache API]
             timetable<-->api
-            timetable<-->db
             scheduler<-->timetable[Timetable Management]
             scheduler-- cycle -->scheduler
         end
@@ -68,7 +66,7 @@ flowchart LR
     style engine_core fill:#FFF,stroke:#333,stroke-width:1px
 ```
 
-- **Event Dispatcher**: Events are issued and consumed in multiple locations of Engine. The diagram shows only a few ones, in order to support the overview.
+(*) **Event Dispatcher**: Events are issued and consumed in multiple locations of Engine. The diagram shows only a few ones, in order to support the overview. Similar to other artifacts, which are not part of this diagram.
 
 ## Prerequisites
 
@@ -79,7 +77,6 @@ Before you begin, ensure you have met the following requirements:
 - [Docker](https://www.docker.com/), optional if you want to run in a container
 - [Python 3.10+](https://www.python.org/downloads/)
 - [Poetry](https://python-poetry.org/)
-- [PostgreSQL 13+](https://www.postgresql.org/)
 
 Ensure that you have also dependencies such as `steering`, `tank`, `dashboard`, `engine-core`, and `engine-api` up and running.