Fix expiry time for Git SHA tagged Docker images

## Summary

Docker images tagged with Git SHA are not expiring as expected on Quay.io. Currently, SHA-tagged images are set to never expire, leading to storage accumulation.

## Current Behavior

Looking at [quay.io/kuadrant/developer-portal-controller](https://quay.io/repository/kuadrant/developer-portal-controller?tab=tags), images with Git SHA tags (e.g., `b2ab687...`) do not have an expiry time set.

## Expected Behavior

Images should automatically expire based on their tags:
- **Images with `main` tag**: Never expire
- **Images with `latest` tag**: Never expire
- **Release tag images** (e.g., `v0.4.0`, `v1.2.3-alpha.1`): Never expire
- **Git SHA tagged images**: Expire after 3 weeks
- **Branch tagged images** (non-main branches): Expire after 3 weeks ✅ (already working correctly)

## Root Cause

The issue is in `.github/workflows/build-image.yaml`. When a push to the `main` branch occurs:

1. The metadata action generates multiple tags for a single build: `main`, `latest`, and the Git SHA
2. The expiry logic evaluates to `expiry=never` because `github.ref_name == "main"`
3. The Docker build uses a single `QUAY_IMAGE_EXPIRY` value for all tags via the `LABEL quay.expires-after` directive
4. **Result**: All tags including the Git SHA inherit `quay.expires-after=never`

This is a Docker/Quay limitation - you cannot set different expiry times for different tags in the same image build because the label is set at the image layer level, not per-tag.

## Possible Solutions

### Option 1: Separate Builds for Different Expiry Requirements
Split the image building into separate jobs with different `QUAY_IMAGE_EXPIRY` build args:
- Job 1: Build and tag with `main` and `latest` (expiry = never)
- Job 2: Build and tag with Git SHA (expiry = 3w)

### Option 2: Use Quay API to Set Tag Expiry Post-Build
After the image is built and pushed, use the Quay API to programmatically set expiration time for the Git SHA tag only.

## Additional Context

- Current Makefile setting: `QUAY_IMAGE_EXPIRY ?= 3w`
- Dockerfile label: `LABEL quay.expires-after=$QUAY_IMAGE_EXPIRY`
- Quay.io documentation on image expiration: https://docs.quay.io/guides/image-expiration.html

Start with .github/workflows/build-image.yaml, then inspect the Dockerfile label and the Makefile’s QUAY_IMAGE_EXPIRY setting. Compare the workflow’s tag and expiry handling with Quay’s image-expiration documentation, and confirm that main, latest, and release tags never expire while Git SHA tags expire after 3 weeks without changing branch-tag behavior.

Written by the indexing model from the issue text.