Add unit tests for Environments, Audit, and Webhooks namespaces (#6)

## Summary
- Add missing unit test coverage for the Environments, Audit, and Webhooks namespaces (raises them from ~0-62% to 91-100%)
- Exclude WebhookBackgroundService/WebhookRetryBackgroundService from coverage (require live DI/DB, disallowed by CLAUDE.md's no-InMemory/WebApplicationFactory rule)

## Test plan
- [x] `dotnet test` full suite passes (646/646)
- [x] Coverage report confirms Environments ~99.5%, Audit 100%, Webhooks ~91%

Reviewed-on: #6

CLAUDE.md

@@ -1,10 +1,10 @@
 # CLAUDE.md
 
-Guidance for Claude Code (claude.ai/code) when working in this repo.
+Guidance for Claude Code (claude.ai/code) in this repo.
 
 ## Project
 
-MicCheck: open source. asp.net, c#, typescript, VueJS. Manages feature flags, projects, environments.
+MicCheck: open source. asp.net, c#, typescript, VueJS. Manage feature flags, projects, environments.
 
 ## Planned Structure
 
@@ -18,27 +18,30 @@ MicCheck: open source. asp.net, c#, typescript, VueJS. Manages feature flags, pr
 - Use latest LTS .NET + latest supported nuget packages for that version
 - Set `langVersion` to latest in all csproj files; enable nullable
 - Organize code by feature/area, not type (e.g. `features` namespace)
-- New features need unit tests covering as much logic as possible (both nunit and jest)
-- Any modified file: evaluate for missing test coverage and that all tests pass
+- New features need unit tests covering logic as much as possible (both nunit and jest)
+- Modified file: check missing test coverage, all tests pass
 
 # Coding
-- Descriptive names for all classes/methods. No generic names: Provider, Manager, Helper
+- Descriptive names all classes/methods. No generic: Provider, Manager, Helper
 - Match formatting/style from `.editorconfig`
-- Wrap lines at 220 characters, leave single line if fewer
-- Place interfaces that are implemented by a single class at the bottom of the class file.  An interface with multiple implementations of an interface should be in a seperate file.
-- Do not use tuples for return types.  Prefer records or classes for multiple values
-- Do not use `sealed` 
+- Wrap lines at 220 chars, single line if fewer
+- Interfaces implemented by single class → bottom of class file. Interface w/ multiple implementations → separate file.
+- No tuples for return types. Prefer records or classes for multiple values
+- No `sealed`
 - Use `record` for data objects, `class` for objects with behavior. Avoid mutable state where possible.
 
 ## Testing
+- Min 70% code coverage, target 90%. Unit tests focus end-user scenarios first.
+- Don't write tests just for coverage. Call out missing coverage rather than cover stuff not valuable to end user.
+- Code not cleanly unit-testable → mark `[ExcludeFromCodeCoverage]` or exclude namespace from coverage in .runsettings file
 - BDD-style unit tests, end-to-end as possible, no external resources (DB, filesystem). e.g. `WhenAUserDoesSomething_ThenAThingAppears`
-- Mock external deps with Moq
-- Mock EntityFramework DBContexts with an extracted interface and Moq.  Do not rely on InMemory provider.
-- New features need unit tests covering as much logic as possible
-- Any modified file: evaluate for missing test coverage- 
+- Mock external deps w/ Moq
+- Mock EntityFramework DBContexts via extracted interface + Moq. Don't rely on InMemory provider.
+- New features need unit tests covering logic as much as possible
+- Modified file: check missing test coverage
 - No "Mock" in mocked object names
 - No Arrange/Act/Assert comments
-- All tests should pass before commit
+- All tests pass before commit
 
 ## Claude
 - Plans = `.md` files in `docs/plans/`. Admin → `docs/plans/admin/`, API → `docs/plans/api/`
@@ -47,4 +50,4 @@ MicCheck: open source. asp.net, c#, typescript, VueJS. Manages feature flags, pr
 - Plan implemented from `docs/plans/<name>.md` → save summary as `docs/plans/<name>_output.md`
 
 ## Stack
-`.gitignore` configured for .NET/Visual Studio (C#, NuGet, MSBuild). Update if stack changes.
+`.gitignore` set for .NET/Visual Studio (C#, NuGet, MSBuild). Update if stack change.