v0.9.8: launch landing sections

[Shaan-alpha]

Summary

Below-the-fold landing sections for launch (hero/search/stats untouched):

• See it in action — clickable example-profile cards (torvalds, gaearon, sindresorhus, antfu, yyx990803, tj) → live /u/<username> reports.
• How it works — deterministic-methodology feature grid.
• Star on GitHub — closing CTA → the repo (static button, no live count).

Shipped as v0.9.8 (1.0.0 reserved for the actual launch).

Test plan

• Frontend lint/tsc clean; vitest 58 passed (+1 smoke test); next build clean, / still ○ Static
• Backend pytest 290 passed (untouched)
• Post-merge: scroll new sections on prod (desktop + mobile); example card → live report; star button → repo