Apply rate limits in LLM service (#15997)

Release Notes:

- N/A

---------

Co-authored-by: Marshall <marshall@zed.dev>
Co-authored-by: Marshall Bowers <elliott.codes@gmail.com>

crates/collab/k8s/collab.template.yml

@@ -85,6 +85,11 @@ spec:
                 secretKeyRef:
                   name: database
                   key: url
+            - name: LLM_DATABASE_URL
+              valueFrom:
+                secretKeyRef:
+                  name: llm-database
+                  key: url
             - name: DATABASE_MAX_CONNECTIONS
               value: "${DATABASE_MAX_CONNECTIONS}"
             - name: API_TOKEN