app: bump version to v1.9-dev (#4192)

This pull request was automatically generated by the 'Tag Minor Full Release' GitHub Action.

- **Target Branch:** `main`
- **New Dev Version:** `v1.9-dev`
- **Stable Release:** `v1.8.0`

## Changes
- Updated version in `app/version/version.go` to `v1.9-dev`

## Next Steps
This PR should be merged after the stable version PR is merged to start the next development cycle.

category: misc
ticket: none

Author: obol-platform

app/version/version.go

@@ -15,7 +15,7 @@ import (
 )
 
 // version a string since it is overwritten at build-time with the git tag for official releases.
-var version = "v1.8-dev"
+var version = "v1.9-dev"
 
 // Version is the branch version of the codebase.
 //   - Main branch: v0.X-dev
@@ -35,6 +35,7 @@ const (
 // Supported returns the supported minor versions in order of precedence.
 func Supported() []SemVer {
 	return []SemVer{
+		{major: 1, minor: 9},
 		{major: 1, minor: 8},
 		{major: 1, minor: 7},
 		{major: 1, minor: 6},