feat(ui): user-story alignment — operator view, point sources, chat consume entry, multi-key failover

[argszero]

Summary

Align the UI prototype (ui/) with docs/user-stories.md per the host's instruction (rant 2026-08-14T22:07:50.623250 — "按用户故事评估并修改 UI 原型 — 补齐 6 处差距"). Closes gaps G1, G2, G4, G5 (G3 already shipped in #20, G6 verified clean — no 1 USD = 1000 点 residue).

• G1 — 平台运营者视图（US-运营1 / US-运营2）: new "平台运营 Operator" tab in the Admin view. ① Platform overview: online status, user count, shared-key count, trade volume, point inflow/outflow; ② top up a user: locate by username/email → enter points (fractional allowed) → confirm → permanent points added + a topup transaction recorded.
• G2 — 点数来源与有效期（US-22 / US-23）: point sources shown grouped with validity badges in both Wallet and Dashboard — gift (每日 1 点 · 当日有效 · 剩 N 天), earn (永久有效), top-up (永久有效).
• G4 — 消费入口（US-6）: each marketplace row gets a "使用 / 消费" button opening a chat-mock modal; sending deducts fractional points (输出参考价 × 0.19M tokens, 2-decimal), records a consume transaction, blocks when balance is insufficient.
• G5 — 多 key 自动故障转移（architecture.md v0.2 §4.2.1）: models with multiple upstream keys show a "多 key · 自动故障转移" badge in the marketplace.

Related Issue

Rant 2026-08-14T22:07:50.623250 (host instruction; no GitHub issue). Docs: docs/user-stories.md v1.7, docs/architecture.md v0.2.

Verification

• node --check ui/js/data.js / ui/js/app.js pass
• All app.js selectors exist in index.html (id cross-check)
• Balance math sanity: POINT_SOURCES sum (1+12470+0) == USER.balance (12471)
• G6: no stale "1 USD = 1000 点" copy in ui/
• cargo test passes
• cargo fmt --check passes

Notes

• Branch: feat/ui-alignment (per CONTRIBUTING.md). One commit, squashed on merge.
• Static prototype only — no backend changes.