Add ASP.NET Core expense tracker prototype with voice-to-transaction UI

[aceofbase199]

Motivation

• Provide a minimal, opinionated expense tracker prototype that is voice-first and easy to extend.
• Offer a compact architecture: a tiny ASP.NET Core minimal API serving a static, interactive front-end.
• Include a simple transcription-to-suggestion flow so users can record audio and confirm generated transactions.
• Keep UI and styles concise and minimalistic to serve as a starting point for further features.

Description

• Add a minimal API (Program.cs) with sample in-memory transactions, GET /api/transactions, POST /api/transactions, and a stub POST /api/transcribe that returns a suggested TransactionSuggestion based on the transcript.
• Add web client under wwwroot including index.html (layout and controls), styles.css (minimal UI styling), and app.js (stats, filters, add flow, voice capture, transcription request and retry/confirm behavior).
• Add project files ExpenseTracker.csproj and appsettings.json, update .gitignore, update README.md describing features and dotnet run usage, and remove the old db.json placeholder.

Testing

• UI preview was served with a lightweight static server and a Playwright script captured a full-page screenshot of the app, which completed successfully.
• Attempt to run dotnet was not possible in this environment because the .NET SDK is not available, so dotnet run was not executed.
• No automated unit tests were added in this prototype.
• Manual browser-based interactions (voice capture flow) are exercised via the front-end code but not covered by automated tests in this PR.

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Codex Task

[chatgpt-codex-connector]

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[chatgpt-codex-connector]

Preserve cents when formatting amounts

The formatter is configured with maximumFractionDigits: 0, so any value with cents is rounded to a whole dollar before display. That means a user-entered 24.90 will show as $25 (and the sample -4.5 shows as -$5), and the totals in the stats will be rounded the same way, which misrepresents the stored amounts. Since the form allows step="0.01", this is a visible accuracy bug for any non-integer input.

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