Refactor: rename OpenAIReceiptParser to AIReceiptParser

Rename to reflect multi-provider support (OpenAI + Anthropic):
- Rename Services/OpenAIReceiptParser.cs to Services/AIReceiptParser.cs
- Update class name from OpenAIReceiptParser to AIReceiptParser
- Update DI registration in Program.cs

The parser now supports both OpenAI and Anthropic models, so the more generic name better reflects its capabilities.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

MoneyMap/Data/MoneyMapContext.cs

@@ -1,6 +1,4 @@
-using System;
-using System.Text.RegularExpressions;
-using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore;
 using MoneyMap.Models;
 using MoneyMap.Services;