docs: add Akash SDL community contribution guide

[listersb]

Summary

• Adds a beginner-oriented Akash SDL walkthrough by Rodri to the Community Contributions collection at src/content/Community_Contributions_Page/akash-sdl-guide/.
• This is a clean successor to Add SDL guide #1097.

Context — why a new PR

#1097 bundled this SDL guide with an unrelated OpenClaw skills guide and went through a long, messy iteration cycle (~14 commits, multiple folder moves, two author identities, DCO round-trip). The OpenClaw portion of that PR is currently breaking CI because ./images/image1.png and ./images/image10.png are referenced from the markdown but were never committed to the branch:

Could not resolve "./images/image10.png" from
"src/content/Community_Contributions_Page/openclaw-skills-on-akash-agents/index.md"

Rather than try to untangle that branch, this PR re-submits only the SDL guide portion, which is build-clean on its own, as a single conventional commit.

Credit for the content goes entirely to Rodri (@rodri-r) — preserved via Co-Authored-By: on the commit and the contributors: frontmatter field. Once this lands, #1097 can be closed.

Changes vs. #1097's SDL guide

• Removed link: "" from frontmatter. The guide appears to be original-to-this-site (no external "original post" exists), so the field is omitted — matching the pattern in cloud-war/index.md. This also suppresses the "Read Original Post" button on the detail page (src/pages/community/contributions/[slug].astro:84), which would otherwise have linked to an empty URL.
• Updated pubDate to 2026-05-17 (today) so the entry sorts correctly on the contributions index.
• Dropped the OpenClaw guide entirely — out of scope for this PR.

Verification

• npm run build passes locally (588 pages, 147s); page renders at dist/community/contributions/akash-sdl-guide/index.html.
• Frontmatter validates against communityContributionsSchema (src/utils/schema/communityContributions.ts).
• No inline image references in the markdown body — only the bannerImage: ./project-banner.png, which is committed.

Test plan

• CI build passes (the failure mode on Add SDL guide #1097 was Vite/rollup unresolved-asset, which doesn't apply here).
• Page renders at /community/contributions/akash-sdl-guide/ with banner image.
• Entry appears on /community/contributions/ index, sorted by pubDate.
• No "Read Original Post" button on the detail page (since link is omitted).
• Author shown as "Rodri" in the sidebar.