feat: add EC2 instances tab, restore TechDocs annotation, and use GitHub catalog URL

- Re-add backstage.io/techdocs-ref annotation to catalog-info.yaml for TechDocs support
- Switch catalog self-registration from local file to GitHub URL
- Add EC2 instances section to AWS Cost entity tab with state-based styling
- Add EC2 backend endpoint using @aws-sdk/client-ec2

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: Ubuntu

app-config.yaml

@@ -325,9 +325,9 @@ catalog:
       rules:
         - allow: [Template]
 
-    # Local catalog entities
-    - type: file
-      target: ../../catalog-info.yaml
+    # Backstage self-registration via GitHub
+    - type: url
+      target: https://github.com/sourcefuse/backstage/blob/main/catalog-info.yaml
       rules:
         - allow: [Component, System, API, Group, User, Resource, Location]
 

catalog-info.yaml

@@ -7,6 +7,7 @@ metadata:
   annotations:
     github.com/project-slug: sourcefuse/backstage
     sonarqube.org/project-key: sourcefuse-cloud/sourcefuse_backstage
+    backstage.io/techdocs-ref: dir:.
   tags:
     - typescript
     - nodejs