feat: Init announcement top banner

[atharvadeosthale]

Summary

• Adds a top banner announcing Init (August 31 - September 4), mirroring the structure of the previous MongoDB partnership banner.
• Inline Init wordmark SVG, one-line copy, and an underlined "Claim your ticket" CTA with arrow; the entire bar links to https://new.appwrite.io/init.
• Mounted in Main.svelte at the same position the MongoDB banner used; new web-top-banner--init SCSS variant.
• Bumps BANNER_KEY to init-banner-03.

Test plan

• Banner renders on home, docs, and pricing pages at the top of the layout
• Clicking anywhere on the banner opens new.appwrite.io/init in a new tab
• Narrow viewport: logo stays left, text wraps beside it, CTA stays on one line

[appwrite]

Appwrite Website

Project ID: 69d7efb00023389e8d27

Sites (1)

Site	Status	Logs	Preview	QR
website 69d7f2670014e24571ca	Ready	View Logs	Preview URL

Website (appwrite/website)

Project ID: 684969cb000a2f6c0a02

Sites (1)

Site	Status	Logs	Preview	QR
website 68496a17000f03d62013	Queued	View Logs	Preview URL

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