ChatGPT

Build me a personal chat client on the OpenAI and Anthropic APIs to replace the text-chat part of ChatGPT Plus. Requirements: - A local web app: Node + Express + better-sqlite3, one page with a streaming reply pane (SSE), a model picker, and a conversation sidebar. - OpenAI and Anthropic keys in .env; system prompt editable per conversation. - Conversations stored in SQLite with FTS5 search; export any thread to Markdown. - File upload for text and PDF (pdf-parse); contents go straight into the context window, no vector database. - A usage footer: tokens and estimated cost per conversation and per month, computed from the usage field in API responses, so I can compare real spend against the $20 flat fee. - Localhost only. No accounts, no telemetry, everything stays on my machine except the API calls. - Out of scope: image generation, voice mode, browsing agents, memory, and mobile apps. Do not attempt any of them; that gap is the subscription. - README: where to get each key, links to current per-token pricing, and state plainly that this replaces text chat only, the frontier model itself cannot be rebuilt.