[Documentation:Developer] Updated Database Diagrams (#700)

The database diagrams were last updated in 2019.

New master db diagram:
<img width="3404" height="2944" alt="database_entity_graph"
src="https://github.com/user-attachments/assets/a4bb2745-b966-4305-a867-39c15ca974a3"
/>

New course db diagram:
<img width="8286" height="13974" alt="database_course_entity_graph"
src="https://github.com/user-attachments/assets/44565c2f-582f-4ab4-bb01-d9b628214568"
/>

Unfortunately, DataGrip was unable to generate the original layout we
had for the course diagram (probably way too big). Here are some
possible alternatives to the layout I selected:
1)
<img width="5258" height="5894" alt="submitty_f25_sample@localhost1"
src="https://github.com/user-attachments/assets/9a88d098-c0a2-41bd-9f34-158be9124d10"
/>

2)
<img width="19182" height="5286" alt="submitty_f25_sample@localhost3"
src="https://github.com/user-attachments/assets/5c4f67d6-f567-41d2-ba8e-e563eb5c4b86"
/>

3)
<img width="9252" height="8630" alt="submitty_f25_sample@localhost4"
src="https://github.com/user-attachments/assets/ab7d1bfa-ff95-4b6e-952e-f6ebc70c7491"
/>

I think the one I chose is the best since it fits the page well. The
others appear too wide or too cluttered.

Author: JManion32

_docs/developer/software_and_system_design/database_design.md

@@ -34,10 +34,10 @@ Note: To add the Submitty server to pgAdmin, follow the [pgAdmin setup instructi
 
 ## Entity-Relation Diagrams
 
-   1. Submitty Database (updated 2019-06-05, see [code for most recent](https://github.com/Submitty/Submitty/blob/master/migration/migrator/data/submitty_db.sql)):
+   1. Submitty Database (updated 2025-08-02, see [code for most recent](https://github.com/Submitty/Submitty/blob/master/migration/migrator/data/submitty_db.sql)):
       ![Database Entity Graph](/images/database_entity_graph.png)
 
-   2. Courses Tables (updated 2019-06-05, see [code for most recent](https://github.com/Submitty/Submitty/blob/master/migration/migrator/data/course_tables.sql)):
+   2. Courses Tables (updated 2025-08-02, see [code for most recent](https://github.com/Submitty/Submitty/blob/master/migration/migrator/data/course_tables.sql)):
       ![Database Entity Graph](/images/database_course_entity_graph.png)
 
    Diagram generated using [DataGrip](https://www.jetbrains.com/datagrip/), by