feat: add in-console Usage Policy summary

[acoshift]

What

Surfaces the new Usage Policy inside the console as a concise, plain-language summary that links out to the authoritative full policy on the website.

• New route /usage-policy (under (auth), no project required) — a page-head + summary panel of 9 bullet points with a prominent Read the full policy link to https://www.deploys.app/usage-policy/.
• New subtle Usage policy link in the sidebar bottom (above the docs/GitHub/Discord/email row), reachable from anywhere.

Why

The full Usage Policy (Acceptable Use Policy) lives on the marketing site (deploys-app/website#23). Logged-in users shouldn't have to leave the console to learn the ground rules, so this gives them the short version in-context with a one-click path to the full text. The summary is the same short version reviewed alongside the website page.

Notes

• Pure static content — no API calls, so no mock fixture needed.
• Uses existing design-system primitives only (page-head, panel is-level-200, button, link, design tokens) — no new components.
• bun lint ✅ and bun check ✅ (0 errors, 0 warnings).

Screenshots

Light	Dark

(sidebar "Usage policy" link is visible bottom-left in both)

[deploys-app]

Preview deleted (PR closed).