feat: initialer Commit des csv2excel CLI-Tools

Go-CLI-Tool zum Konvertieren von CSV-Dateien in Excel (.xlsx),
mit Mage-Build-System und Architektur-Dokumentation.

docs/architecture.md

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+# Architecture
+
+## Overview
+
+Single-file tool — entire application logic lives in `main.go`.
+
+- **`main()`**: Parses flags (`-sep`, `-enc`, `-o`), iterates over input CSV files, creates one Excel sheet per file using the filename (without extension) as the sheet name, writes all rows, saves the output `.xlsx`.
+- **`detectDelimiter()`**: Auto-detects the CSV delimiter by counting `;`, `,`, and `\t` occurrences in the first line. Falls back to `;` on error.
+
+Key behaviors:
+- Sheet names are truncated to 31 characters (Excel limit)
+- Encoding `windows1252` wraps the file reader with a Windows-1252 decoder
+- `csvReader.LazyQuotes = true` for tolerance with malformed CSV files
+- The first sheet renames "Sheet1"; subsequent sheets are created fresh
+
+## Version Injection
+
+Version info is injected at build time via ldflags from git tags:
+- `internal/version.Version` — from `git describe --tags --always`
+- `internal/version.Commit` — from `git rev-parse --short HEAD`
+- `internal/version.BuildDate` — from `date -u`
+
+## Dependencies
+
+- `github.com/xuri/excelize/v2` — Excel file creation/manipulation
+- `golang.org/x/text` — Character encoding (Windows-1252 support)