feat: add Cursor rules for project onboarding

[Sopor10]

Summary

• Add 6 comprehensive Cursor rules in .cursor/rules/\ to onboard this repository for AI-assisted development
• project-overview.mdc: Architecture overview, project structure, tech stack summary (always applies)
• csharp-conventions.mdc: C# coding style, formatting (CSharpier), architecture constraints, domain patterns (applies to *.cs)
• blazor-patterns.mdc: Blazor WASM conventions, Fluxor state management, Radzen UI, component organization (applies to *.razor)
• testing.mdc: Test frameworks (NUnit, FluentAssertions, Verify, Playwright, Reqnroll), patterns, architecture tests (applies to test files)
• build-and-ci.mdc: Build prerequisites, local dev commands, CI pipeline overview, package management (always applies)
• mcp-server.mdc: MCP tool conventions, Filter DSL overview, how to add new tools (applies to MCP server files)

Motivation

These rules give Cursor (and any AI agent) the context it needs to make correct, idiomatic changes aligned with this project's architecture, patterns, and tooling.

Test plan

• Rules are valid .mdc\ files with correct frontmatter
• Content accurately reflects the codebase structure and conventions
• Verify rules appear correctly in Cursor's rule picker
• Open a file matching each glob and confirm the relevant rule activates

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud