fix(api): stop a failed surface delete from leaving a duplicate row

[catomean]

Summary

• The surfaces upsert (POST /api/surfaces) deletes the existing surface row for a project, then inserts the new one — but never checked whether the delete succeeded.
• If the delete silently failed (RLS misconfig, transient DB error), the insert left two rows for one project_id. Every later GET /api/surfaces would then 500, since it relies on .maybeSingle(), which errors on more than one matching row.
• Same unchecked-error pattern as PR fix(compose): surface failed figure saves instead of discarding them silently #36/fix(nav): the app knew which page you were on and never said it #37/fix(figures): the styled upload could fail without saying so #39/fix(api): stop surfacing DB errors as "no surface/composition yet" #40/fix(api): stop a swallowed query error from mis-numbering compositions #43 — this was flagged as a known follow-up in the handoff for fix(api): stop a swallowed query error from mis-numbering compositions #43 but scoped out to keep that PR to one fix.

Test plan

• npx tsc --noEmit — clean
• npm run lint — 0 errors (8 pre-existing warnings, unrelated)
• npm run test — 96 passed, 0 failed (error-shape.test.ts and query-error-checked.test.ts both pass against the new code)

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