[luke-song]

Summary

Adds a Share my success button on the workout complete screen (next to Go to my profile) so users can generate a social-friendly summary image client-side.

Closes #54.

What changed

• New ShareWorkoutCard (4:5 / 600×750) with date, muscles worked, exercise count, motivational message, and workout.cool logo
• New ShareWorkoutButton that captures the card with html-to-image, then uses the Web Share API with a PNG file when available (mobile), otherwise downloads the image
• Wired into the actual end-of-session UI in WorkoutStepper (and the congrats branch in WorkoutSessionSets for consistency)
• Locale strings for en / fr / es / pt / ru / zh-CN
• Adds html-to-image dependency

Why this approach

• After completeWorkout(), isWorkoutActive becomes false, so the visible congrats screen is in WorkoutStepper — not only WorkoutSessionSets. This PR puts the share CTA where users actually land.
• Uses formatDate from shared/lib/date (FSD) and a plain <img> for the logo so html-to-image captures reliably.
• No server-side image rendering.

How to test

1. Start a workout (equipment → muscles → exercises → start).
2. Finish the session (complete sets / finish session).
3. On the congrats screen, confirm Share my success appears next to Go to my profile.
4. Click share:
   • Mobile / share-capable browsers: native share sheet with the PNG.
   • Desktop: PNG downloads as workout-cool-summary.png.
5. Confirm the image includes date, muscle pills, exercise count, logo, and “Keep going!”-style motivation.

Notes

There is an existing open PR (#250) for the same issue; this implementation differs mainly by wiring the button into the WorkoutStepper congrats screen users actually see after finish, plus multi-locale strings and FSD date formatting.

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