chore: housekeeping for v0.3 prep

- Pin KUBESOLO_VERSION in versions.env (was soft-defaulted in fetch-components.sh)
- Gitignore screenshots, macOS resource forks, and common image extensions
- Update README roadmap: x86_64 stable, ARM64 generic in progress (v0.3),
  ARM64 RPi paused pending hardware
- Add docs/ci-runners.md documenting the Odroid arm64-linux Gitea runner

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

build/config/versions.env

@@ -9,6 +9,9 @@ TINYCORE_ISO=CorePure64-${TINYCORE_VERSION}.iso
 TINYCORE_ISO_URL=${TINYCORE_MIRROR}/${TINYCORE_VERSION%%.*}.x/${TINYCORE_ARCH}/release/${TINYCORE_ISO}
 
 # KubeSolo
+# Pinned release tag from https://github.com/portainer/kubesolo/releases.
+# Bump here and re-run `make fetch` to pull a new version.
+KUBESOLO_VERSION=v1.1.0
 KUBESOLO_INSTALL_URL=https://get.kubesolo.io
 
 # Build tools (used inside builder container)