Reword the default cookie banner copy

[dev-geddy]

The seeded default led with the cost and gave no reason to accept, so almost nothing gets measured. Same facts, different order.

Before

We use cookies to measure how this site is used, via Google Analytics. Analytics only runs if you accept.

After

Can we count your visit? It shows us which pages actually help people — we only ever look at totals, and never use it for ads. It runs on Google Analytics cookies, and only if you accept.

Changes:

• packages/db/migrations/0008_reword_cookie_banner.sql — custom migration. Guarded WHERE "cookieBannerText" = <the 0006 literal>, so an operator-edited banner is never clobbered (L2-ANALYTICS-08) and a re-run matches nothing. 0006 is left untouched — applied migrations are immutable; a fresh DB runs 0006 then 0008 and lands on the new copy.
• analytics-gate.tsx — FALLBACK_TEXT mirrors the new seed.
• docs/notes/analytics.md — the migration + why the copy reads the way it does.

Copy-only; no behaviour change. Claims stay scoped to our use of the data — deliberately no promises about what Google does with it, since an operator can enable Signals/ads features and make them false. Layout untouched: Decline and Accept, one click each, same bar (EDPB wants reject equally easy, not identically styled).

Verified against a migrated local DB, and headless at 1440×900 (light + dark) and 390×780 with the config route stubbed: banner renders, zero googletagmanager requests before Accept, one after, banner gone and granted persisted, no console errors/warnings, no horizontal scroll. Typecheck + lint pass.

Note this only lifts the accept rate — visitors who ignore the banner are still unmeasured. The coverage fix is a cookieless provider, proposed separately.