[G6] Reward feedback: unlock animations and satisfying micro-interactions

The part that actually makes the app feel gamified. Split out of the display tickets so the surface can ship without waiting on art direction.

Depends on: [G4] Profile progression display, [G5] Achievements screen.

Scope

• Define every micro-interaction explicitly — what plays, when, and why: unlock toast, level-up, season/series completion, progress rings, "two episodes left" nudge.
• Set the cursor deliberately: rewarding, never kitsch, never overdone. This calibration is the actual deliverable, the code is the easy part.
• Sound, if any, off by default.
• Respect the "hide my progression" setting and prefers-reduced-motion.

Rule that constrains this ticket

No loss pressure. The streak is displayed; its loss is never notified, and there is no streak-freeze token to collect. No notification whose only purpose is to bring the user back.