chore(ci): cleanup CI system

[albttx]

No description provided.

[netlify]

✅ Deploy Preview for dither-staging ready!

Name	Link
🔨 Latest commit	f3b3597
🔍 Latest deploy log	https://app.netlify.com/projects/dither-staging/deploys/69e24bbb2a3e2100083aa77c
😎 Deploy Preview	https://deploy-preview-518--dither-staging.netlify.app
📱 Preview on mobile	Toggle QR Code... Use your smartphone camera to open QR code link.

---

To edit notification comments on pull requests, go to your Netlify project configuration.

[jeronimoalbi]

Why are the mainnet-reader-main.yml, mainnet-api-main.yml and the similar "testnet" ones deleted?

[albttx]

Why are the mainnet-reader-main.yml, mainnet-api-main.yml and the similar "testnet" ones deleted?

These workflows were deleted because they were redundant. The docker.yml workflow already handles everything they did, but in a simpler, unified way:

Before (old setup):

• mainnet-api-main.yml → pushed to GCP on api/v* tags
• mainnet-reader-main.yml → pushed to GCP on reader/v* tags
• testnet-api-main.yml → pushed to GCP on every push to main
• testnet-reader-main.yml → pushed to GCP on every push to main

After (simplified):

• docker.yml → builds both api-main and reader-main, pushes to GHCR:
  • On push to main → tagged as latest
  • On v* tags → tagged with the version (e.g., v1.2.3)

The key changes:

1. Single workflow instead of 4 separate ones
2. Single tag format (v*) instead of separate api/v*, reader/v* tags
3. GHCR (GitHub Container Registry) instead of GCP Artifact Registry — no need for GCloud auth secrets

[jeronimoalbi]

Related to #513