[Observability 10/10] Add OTEL metrics to controller reconcilers

[concaf]

Context

Extend OTEL metrics instrumentation to the 7 controller reconcilers. The controller already has built-in controller-runtime metrics (workqueue depth, reconcile duration) but no custom application-level metrics.

Scope (to be detailed)

• Add custom metrics to controller reconcilers:
  • Reconcile error counter by CR name and controller
  • CR state duration (time spent in non-ready state)
  • Stage processing metrics
• Wire telemetry init into cmd/main.go (controller entry point)
• Leverage existing controller-runtime metrics registry where possible

Controllers to instrument (7 total)

• ControllerConfigReconciler
• UnstructuredDataPipelineReconciler
• DocumentProcessorReconciler
• ChunksGeneratorReconciler
• VectorEmbeddingsGeneratorReconciler
• SourceCrawlerReconciler
• DestinationSyncerReconciler

Use cases enabled

B6 (repeated reconcile errors), B7 (CR stuck non-ready), C6 (reconcile duration)

Depends on

• [Observability 1/10] Add OTEL metrics foundation — telemetry package + main.go wiring #308 (telemetry foundation)
• Phase 1 MCP server issues — to validate the pattern before applying to controller