Group Program.cs DI/service registration into extension methods #291

Problem

src/Cluckwork.Api/Program.cs is ~1026 lines. Endpoint mapping is already modular (each feature has its own Map<Feature>Endpoints extension), and the run-then-exit CLI commands are being extracted separately (#288). The remaining bulk is the long inline service-registration block — dozens of builder.Services.Add… calls for persistence/EF, identity/JWT, telemetry/OTel, rate limiting, feature handlers/validators/repositories, health checks, etc.

Proposal

Group the registrations into AddCluckwork*(this IServiceCollection, IConfiguration) extension methods by concern, e.g.:

• AddCluckworkPersistence (AppDbContext, interceptors, repositories)
• AddCluckworkIdentity (Identity, JWT, AdminRecoveryService)
• AddCluckworkTelemetry (OpenTelemetry traces/metrics, Serilog wiring)
• AddCluckworkRateLimiting
• AddCluckworkFeatures (handlers + FluentValidation validators + feature repos)
• AddCluckworkHealthChecks

So the ConfigureServices section of Program.cs reads as a handful of builder.Services.AddCluckwork*() calls, keeping the wiring discoverable and the bootstrapper small.

Constraints

• Pure, behaviour-preserving refactor — no registration added/removed/reordered in a way that changes resolution; the full suite must stay green unchanged.
• Follow the existing Map<Feature>Endpoints extension-method convention.
• Keep it separable from the CLI-command extraction (feat(api): migrate command + prod migration split (#263) + extract CLI commands into a testable layer #288) — this issue is service registration only.

Tech-debt / maintainability. Relates to the CLI-extraction work on #288.