Replace legacy installation graphics with mermaid.js diagrams (#22229)

docs/installation/index.md

@@ -35,7 +35,34 @@ The following sections detail how to set up a new instance of NetBox:
 
 Below is a simplified overview of the NetBox application stack for reference:
 
-![NetBox UI as seen by a non-authenticated user](../media/installation/netbox_application_stack.png)
+```mermaid
+flowchart TB
+    nginx["<span style='color:#fff'><b>nginx / Apache</b><br/>HTTP reverse proxy</span>"]:::red
+    gunicorn["<span style='color:#fff'><b>gunicorn</b><br/>WSGI HTTP server</span>"]:::orange
+    rqworker["<span style='color:#fff'><b>rqworker</b><br/>Background worker</span>"]:::pink
+    netbox["<span style='color:#fff'><b>NetBox</b><br/>Django application</span>"]:::blue
+    django["<span style='color:#fff'><b>Django</b><br/>Python application framework</span>"]:::green
+    storage["<span style='color:#fff'><b>Storage Driver</b><br/>Static asset storage</span>"]:::gray
+    postgres["<span style='color:#fff'><b>PostgreSQL</b><br/>Relational database</span>"]:::teal
+    redis["<span style='color:#fff'><b>Redis</b><br/>In-memory store</span>"]:::purple
+
+    nginx --> gunicorn
+    nginx --> storage
+    gunicorn --> netbox
+    rqworker --> netbox
+    netbox --> django
+    django --> postgres
+    django --> redis
+
+    classDef red fill:#b91c1c,stroke:#7f1d1d,color:#fff
+    classDef orange fill:#c2410c,stroke:#7c2d12,color:#fff
+    classDef pink fill:#a21caf,stroke:#701a75,color:#fff
+    classDef blue fill:#1d4ed8,stroke:#1e3a8a,color:#fff
+    classDef green fill:#15803d,stroke:#14532d,color:#fff
+    classDef gray fill:#4b5563,stroke:#1f2937,color:#fff
+    classDef teal fill:#0f766e,stroke:#134e4a,color:#fff
+    classDef purple fill:#6d28d9,stroke:#4c1d95,color:#fff
+```
 
 ## Upgrading
 

docs/installation/upgrading.md

@@ -4,7 +4,20 @@ Upgrading NetBox to a new version is pretty simple, however users are cautioned
 
 NetBox can generally be upgraded directly to any newer release with no interim steps, with the one exception being incrementing major versions. This can be done only from the most recent _minor_ release of the major version. For example, NetBox v2.11.8 can be upgraded to version 3.3.2 following the steps below. However, a deployment of NetBox v2.10.10 or earlier must first be upgraded to any v2.11 release, and then to any v3.x release. (This is to accommodate the consolidation of database schema migrations effected by a major version change).
 
-[![Upgrade paths](../media/installation/upgrade_paths.png)](../media/installation/upgrade_paths.png)
+```mermaid
+block-beta
+    columns 10
+    v29["v2.9"] v210["v2.10"] v211["v2.11"] v30["v3.0"] v31["v3.1"] dots["..."] v36["v3.6"] v37["v3.7"] v40["v4.0"] v41["v4.1"]
+    v2arrow["<span style='color:#fff'>To any v2.x release ➜</span>"]:3 space:7
+    space:2 v3arrow["<span style='color:#fff'>To any v3.x release ➜</span>"]:6 space:2
+    space:7 v4arrow["<span style='color:#fff'>To any v4.x release ➜</span>"]:3
+    classDef orange fill:#b45309,stroke:#78350f,color:#fff
+    classDef green fill:#0f766e,stroke:#134e4a,color:#fff
+    classDef blue fill:#1d4ed8,stroke:#1e3a8a,color:#fff
+    class v2arrow orange
+    class v3arrow green
+    class v4arrow blue
+```
 
 !!! warning "Perform a Backup"
     Always be sure to save a backup of your current NetBox deployment prior to starting the upgrade process.