Reorder community links and add member milestone

[ashryanbeats]

Summary

• move the existing Meetup, Discord, GitHub, and Contact links directly below first-meetup onboarding
• rename the section to Community links without changing its destinations
• cache the Meetup member count, round it down to 25-member milestones, and show neutral social proof in the hero
• preserve the last valid member count when a refresh omits it
• update the homepage roadmap to reflect the revised direction

Verification

• npm run check
• npx astro build
• English and Japanese DOM/link review
• desktop 1440px and mobile 390px visual review
• mobile horizontal overflow check (390px scrollWidth/clientWidth)

[cloudflare-workers-and-pages]

Deploying kyoto-tech-github-io with    Cloudflare Pages

Latest commit:	1220f35
Status:	✅  Deploy successful!
Preview URL:	https://2bd0a123.kyoto-tech-github-io.pages.dev
Branch Preview URL:	https://dev-community-links-page-ord.kyoto-tech-github-io.pages.dev

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