Add claude file

CLAUDE.md

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+# CLAUDE.md
+
+This file provides guidance to Claude Code (claude.ai/code) when working with code in this repository.
+
+## Commands
+
+```bash
+# Build
+dotnet build
+
+# Run (dev server at http://localhost:5225)
+cd Schaad.Accounting.UI && dotnet run
+
+# Publish
+dotnet publish -c Release
+```
+
+There are no automated tests or lint commands.
+
+## Architecture
+
+**AccountingNext** is a Swiss personal accounting app built with ASP.NET Core 9 + Blazor (interactive server-side rendering) and Microsoft Fluent UI. Data is stored as XML files on disk — no database.
+
+### Projects
+
+| Project | Role |
+|---|---|
+| `Schaad.Accounting.UI` | Blazor web app — pages, dialogs, layout |
+| `Schaad.Accounting.Services` | Business logic — balances, FX conversion, file import, charts |
+| `Schaad.Accounting.Db` | Repository layer — XML serialization/deserialization |
+| `Schaad.Accounting.Common` | Shared models, DTOs, interfaces |
+
+### Data flow
+
+```
+Blazor Pages/Dialogs (UI)
+  → Services (ViewService, FileService, ChartService)
+  → Repositories (AccountRepository, TransactionRepository, …)
+  → XML files: {DataPath}/{year}/{mandator}/Data/*.xml
+```
+
+Data is multi-year and multi-mandator. Each combination has its own directory under `DataPath` (configured in `appsettings.Development.json`). When a new year is opened, the previous year's data is copied as the starting point.
+
+### Key services
+
+- **ViewService** — aggregates account balances, applies FX rates, builds datasets for the UI
+- **FileService** — imports bank statements (MT940, CAMT053 via external `Schaad.Finance.dll`), parses PDFs, manages backups
+- **ChartService** — produces data for Plotly charts (assets, spendings over time)
+- **SettingsService** — manages the active year, mandator, and file paths
+
+### UI structure
+
+Pages live in `Schaad.Accounting.UI/Components/Pages/`. Each page typically has a companion `Dialogs/` subfolder with Fluent UI dialog components for CRUD operations. The app is hardcoded to the `de-CH` culture.
+
+### Key external dependencies
+
+- `Microsoft.FluentUI.AspNetCore.Components` — UI components (FluentDataGrid, FluentDialog, etc.)
+- `Plotly.Blazor` — charts
+- `FreeSpire.PDF` — PDF parsing for bank statement imports
+- `Schaad.Finance.dll` / `Schaad.Finance.Api.dll` — proprietary DLLs for MT940/CAMT053 parsing and FX rate lookups (FixerIo API key in `appsettings.Development.json`)
+
+### Domain constants
+
+`ClassIds` in `Schaad.Accounting.Common` defines the Swiss accounting chart-of-accounts classes: Activa=1000, Passiva=2000, Income=3000, Expenses=4000.