Add PocketBase client with contracts and sharp build tooling

.editorconfig

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+# EditorConfig for the Elternbeirat solution.
+# https://editorconfig.org  /  https://learn.microsoft.com/dotnet/fundamentals/code-analysis/code-style-rule-options
+#
+# Code-style rules are added here over time. Kept intentionally minimal for now;
+# the .NET analyzers (see Directory.Build.props) already run at their sharpest.
+
+root = true
+
+[*]
+charset = utf-8
+end_of_line = crlf
+insert_final_newline = true
+trim_trailing_whitespace = true
+indent_style = space
+
+[*.{cs,csproj,props,targets}]
+indent_size = 4
+
+[*.{json,yml,yaml}]
+indent_size = 2
+
+[*.cs]
+# CA1716 flags type names that collide with Visual Basic keywords (e.g. Event).
+# This app is not consumed from VB, and Event/Post are the project's deliberate
+# domain names (see CLAUDE.md: "im Code Event, nicht Termin"). Renaming would
+# break that convention for a problem this codebase does not have.
+dotnet_diagnostic.CA1716.severity = none
+
+# CA1515 suggests making types internal because an app's types are not referenced
+# from outside its assembly. That is a library-author rule with no benefit here:
+# this is an application, not a reusable package. Razor components (Home, PostList,
+# ...) must stay public so Blazor can render them, and the Contracts records are
+# consumed from another project. Turning types internal would gain nothing.
+dotnet_diagnostic.CA1515.severity = none
+
+# CA1062 wants public methods to null-check their arguments. The public surface
+# here is DI constructors and Blazor components, never called by foreign code with
+# raw arguments; the container always supplies its dependencies. With #nullable on,
+# a non-nullable parameter already carries the "never null" contract in its type.
+dotnet_diagnostic.CA1062.severity = none
+
+# CA2007 (ConfigureAwait) targets libraries with a SynchronizationContext (WinForms,
+# WPF, classic ASP.NET). ASP.NET Core has none, so ConfigureAwait(false) would be
+# pure noise here. Microsoft's own project templates disable this rule.
+dotnet_diagnostic.CA2007.severity = none
+
+# CA1812 flags types "never instantiated". The JSON DTOs (e.g. RecordList<T>) are
+# only created by the deserializer via reflection, which the analyzer cannot see.
+# This is a known false positive for deserialization types.
+dotnet_diagnostic.CA1812.severity = none
+
+# CA1724 flags a type name that matches part of its namespace (Home in
+# ...Features.Home). That collision is a deliberate result of the feature-folder
+# layout and is harmless (Blazor routing is not namespace-based). Renaming would
+# break the folder convention for no benefit.
+dotnet_diagnostic.CA1724.severity = none