M9-S4b: seller listing management write operations

[erikshafer]

Summary

• Create-draft form at /listings/new — 10-field form with react-hook-form + Zod validation; Flash/Timed conditional duration visibility; extended-bidding toggle with conditional trigger-window/extension fields; duration presets dropdown (1h–7d); shouldUnregister: true for clean conditional field handling
• Edit-draft dialog — modal overlay on Draft-status listing cards; 3 mutable fields (title, reservePrice, buyItNowPrice) pre-populated from current values; PUT /api/selling/listings/draft
• Submit-for-publication button — on Draft-status listings; POST /api/selling/listings/submit; auto-approval chain transitions to Published immediately
• Mutation hooks — useCreateDraft, useEditDraft, useSubmitListing with TanStack Query invalidation on success
• shadcn/ui additions — Input, Label, Select, Checkbox components
• 35 new tests — form schema validation (17), create-listing page (7), mutation payload transformation (4), listings page actions (7); seller total 55 (was 20)
• Live HTTP smoke — full journey verified: session → register → create Flash draft → query → edit → submit → Published → create Timed draft (7-day duration) → submit → 2 Published listings

Zero backend changes. Bidder (25) and ops (47) test baselines unchanged.

Test plan

• npm run build — seller app builds clean (tsc + vite)
• Seller Vitest: 55 pass (was 20, +35)
• Bidder Vitest: 25 pass (unchanged)
• Ops Vitest: 47 pass (unchanged)
• .NET build: 0 errors, 2 warnings (baseline)
• .NET tests: 326 pass (untouched)
• Live HTTP smoke against Aspire: create → edit → submit for both Flash and Timed
• CI green