feat(site): complete playground and branding

[Seungpyo1007]

What & why

Completes the homepage's published-resource surface:

• adds laptops, monitors, and software to the Playground selector and endpoint list; and
• replaces the TechAPI header and footer placeholder mark with the supplied brand image.

Games remain intentionally absent because the Pages deployment excludes the game dump.

Source

Brand image supplied for this repository. Resource availability verified against the deployed static v1 index and list endpoints.

Checklist

• Verified laptops, monitors, and software list endpoints and detail slugs
• Kept games excluded from the public Pages API
• No dataset records or TechEngine files changed

Closes #19