Add ZIP-wrapped CAMT parsing and real bank file tests

- Support parsing camt.052 ZIP archives in CamtParser and BankingService
- Add CamtZipParserTests for ZIP parsing (single/multi/malformed/empty cases)
- Add CamtRealFileTests: integration tests for real bank exports (ZIP, XML, CAMT, MT940, STA) in git-ignored test data dir
- Update .gitignore and add README.md for test data usage
- Copy test data files in Fuchs.Tests.csproj; add .gitkeep
- Refactor BankingService CAMT mapping logic
- Overhaul connection string config: use {username}/{password} tokens, resolve from secrets at runtime, update appsettings and Key Vault keys

.gitignore

@@ -1,4 +1,4 @@
-# Visual Studio
+# Visual Studio
 .vs/
 *.user
 *.suo
@@ -38,3 +38,11 @@ secrets.cache
 
 # Secret values file (never commit)
 Scripts/secrets.json
+
+# Banking test data (sensitive real bank export files — never commit)
+Fuchs.Tests/TestData/Banking/*.zip
+Fuchs.Tests/TestData/Banking/*.xml
+Fuchs.Tests/TestData/Banking/*.camt
+Fuchs.Tests/TestData/Banking/*.sta
+Fuchs.Tests/TestData/Banking/*.mt940
+Fuchs.Tests/TestData/Banking/*.txt