Import income from a CSV/TSV/text export (Stripe, PayPal, Square, Cash App, Venmo, OnlyFans, Patreon, Clips4Sale, Ko-fi, Gumroad, Etsy, Uber/Lyft/DoorDash driver exports, bank statements, and similar; max 500 KB). Same two-step contract as add_income_from_file: STEP 1 call with csvContent and WITHOUT confirm parses the file with the same platform-agnostic importer as the app's Add Income screen (platform detection, fee handling, refunds, source aliases, ISO dates) and returns a duplicate-checked preview with a previewId. NOTHING is saved in step 1. Show the user the parsed rows and duplicates, then STEP 2 call again with confirm: true and the previewId to write exactly those rows, optionally with user-approved selectedIndexes, keepBothIndexes, rowEdits, tag, or bulkNote. Flagged duplicates are skipped unless the user explicitly keeps them. The preview expires after 15 minutes and an expired or unknown previewId never writes. After a successful confirm, show the returned spreadsheetUrl and reviewIncomeUrl.