feat: add preprod observability foundation

docs/TASKS/observability/001-observability-foundation.md

@@ -0,0 +1,44 @@
+# Observability 001: Preprod Foundation
+
+## Goal
+
+Add the first preproduction observability foundation for Socialize so the operator can tell whether the app is healthy and whether core workflows are being used.
+
+## Feature Spec
+
+- `docs/FEATURES/observability.md`
+
+## Scope
+
+- Add backend OpenTelemetry registration for traces and metrics.
+- Add structured JSON console logging with request correlation context.
+- Add aggregate custom counters for core usage events.
+- Expand health endpoints with liveness and readiness checks.
+- Add an optional Docker Compose observability overlay for Grafana, Prometheus, Loki, Tempo, and Alloy.
+- Add basic Grafana datasource/dashboard provisioning.
+
+## Likely Files
+
+- `backend/src/Socialize.Api/Program.cs`
+- `backend/src/Socialize.Api/ApplicationRegistration.cs`
+- `backend/src/Socialize.Api/Infrastructure/Observability/*`
+- selected backend handlers for usage counters
+- `backend/src/Socialize.Api/Socialize.Api.csproj`
+- `deploy/observability/*`
+- `README.md`
+
+## Out Of Scope
+
+- Client-facing analytics or status page.
+- Frontend behavioral analytics.
+- Cloud telemetry providers.
+- Long-term telemetry retention policy.
+- Full product analytics warehouse.
+
+## Validation
+
+```bash
+dotnet build backend/Socialize.slnx
+dotnet test backend/Socialize.slnx
+docker compose -f deploy/compose.yml -f deploy/observability/compose.observability.yml config
+```