Claude

Build me a personal chat client on the Anthropic API to replace my Claude Pro subscription with per-token billing. Requirements: - A local web app: Node + Express + better-sqlite3, streaming replies over SSE, a conversation sidebar, Markdown rendering with marked. - Anthropic API key in .env; model picker with Sonnet as the default and Opus on demand; system prompt editable and saved per project. - Projects: a project groups conversations and holds a few reference docs (plain text or PDF via pdf-parse) prepended as context for every chat inside it. - Use prompt caching on the project docs to cut token costs, the API supports it directly. - SQLite FTS5 search across all conversations; export any thread to Markdown. - A cost meter per conversation plus a monthly total from the API usage fields, so the keep-paying-or-not decision is a number, not a feeling. - Localhost only, no accounts, no telemetry. - Out of scope: artifacts, mobile apps, and agent features. If the cost meter shows heavy use, flat-rate Pro or Max wins; include that comparison logic in the README. - README: key setup, a link to current per-token prices, and state that the model is the product; this wrapper only changes how I pay for it.