[AK-676] X rebrand + profile CTA + posting-bot update

[robinbraemer]

Migrated from Linear: AK-676

GitHub is the canonical source of truth. The Linear issue is archived.

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What

Rename @cnap to @Akua. Swap profile pic, banner, bio. Update profile CTA button link. Update posting-bot config + templates.

Bot changes

• Replace hardcoded "CNAP" strings
• Update auto-reply templates
• Update OAuth app name + redirect URI if needed
• Swap "CNAP" hashtags for "Akua"

Done when

• Handle is @Akua (or new account live + old archived)
• Profile pic, banner, bio updated
• Profile CTA button points to final akua domain
• Pinned tweet is the rebrand announcement
• Bot test-posts successfully under new branding
• Bot repo PR merged + deployed