fix: restore appsettings.Development.json — a test loads it non-optionally

[mforce]

Reverts #591. main is currently broken by it — three integration tests fail, and PR #588's CI surfaced it because PR runs test the branch merged into main.

What broke

tests/Cluckwork.Api.IntegrationTests/ProductionLogFormatTests.cs:318:

builder.AddJsonFile($"appsettings.{environment}.json", optional: false);

Non-optional. #591 untracked src/Cluckwork.Api/appsettings.Development.json (preserving its content as appsettings.Development.example.json), so the file is absent from a clean checkout and the three environment: "Development" cases throw:

System.IO.FileNotFoundException : The configuration file
'appsettings.Development.json' was not found and is not optional.

Failing: Non_production_configurations_bind_a_template_renderer(Development), Development_keeps_the_human_template_and_no_formatter, Exactly_one_console_sink_is_configured(Development). 1418 passed, 3 failed.

Why the revert rather than a fix-forward

Making the test's load optional, or repointing it at the .example.json, would keep CI green while deleting the guarantee. Those tests exist for #404: they assert the shipped Development config binds a template renderer and exactly one console sink — a formatter left beside a template is silently bound instead of it, which is the defect #404 records. If the file is not in the repo, there is no shipped Development config to assert about, and #404's Development-side guarantee becomes unverifiable.

So the file is load-bearing as a tracked artifact, not merely as content. #591 was wrong.

How I got it wrong

I claimed "nothing referenced the tracked file" after grepping Cluckwork.Api.csproj, Dockerfile, .github/, deploy/, tools/, and *.md + docs/. I never grepped tests/. A directory-filtered enumeration reported complete — the exact failure mode AGENTS.md #394 describes for contract changes ("list the references repo-wide, with no file-type filter"), applied to a file removal instead of a rename.

Verified after reverting: dotnet test --filter ProductionLogFormatTests → 15 passed, 0 failed.

The original concern still stands, and needs the other fix

#591 existed because a local Postgres connection string had been edited into that tracked file, one git commit -a from being committed to a GitGuardian-scanned repo. Untracking was the wrong remedy. The right one is the one AGENTS.md already prescribes, and UserSecretsId is already configured for it:

dotnet user-secrets --project src/Cluckwork.Api set "ConnectionStrings:Default" "..."

There is now hard evidence for why that is the only option: the file cannot be untracked without breaking a guard.