feat(web): add looping localized welcome typewriter

[bobleer]

Summary

Replace the welcome page's three-phrase fade, which stops on the final phrase, with an infinite typewriter loop. Each complete phrase is typed, held for 2.2 seconds, and erased before the next phrase, with a blinking cursor.

Keep the logo and OpenBitFun title stationary by reserving space for the longest phrase. Expand the rotation to seven phrases and localize all copy in Simplified Chinese, Traditional Chinese, and English, including “创造不可能。” / “Create the impossible.” and “让梦想开出花。” / “Let dreams bloom.” New phrases are translated as complete sentences rather than concatenated with the English “space.” suffix.

Type and Areas

Type: UI/UX feature

Areas: Web UI welcome scene, i18n resources

Motivation / Impact

Make the tabless welcome surface feel more lively while preserving its existing branding and theme tokens. Pause typing while the document is hidden, restart with translated copy when the locale changes, and show the static invitation with no blinking cursor when reduced motion is preferred. Screen readers retain a stable heading instead of receiving per-character updates.

Verification

• pnpm run lint:web — passed after correcting the timer callback declaration; only an existing unrelated editor warning remains.

• pnpm run check:web — passed, including type checking and appearance/theme governance.

• pnpm run i18n:audit — passed with zero warnings.

• pnpm run motion:audit — reviewed the informational inventory; the welcome cursor has a local reduced-motion override. The report's existing unrelated PortForwardDialog finding is unchanged.

• git diff --check — passed.

• Local browser preview — inspected the welcome page, cursor, phrase rotation, and reserved layout width; confirmed seven localized phrases load.

• Remote workspace, Remote Control, Peer Device Mode, and Detached Dispatch were not exercised. This change is presentation-only and adds no host calls or protocol changes.

Reviewer Notes

AI-assisted implementation; testing level: lightly tested (local automated checks and browser inspection, no full desktop/platform or remote matrix). No new dependencies or persisted data changes.

Checklist

• This PR is focused and does not include secrets, temporary prompts, generated scratch files, or unrelated artifacts.
• Relevant verification is recorded above, or skipped checks are explained.
• User-facing strings, docs, and locales are updated where applicable.