fix: template build panic handling

[dobrac]

Fix template build panic handling to properly fail the build and report the error.

---

Note

Recover from panics during template builds, report them via telemetry with context, and mark the build as failed with a user-facing error.

• Template Build (orchestrator):
  • Builder (internal/template/build/builder.go): Add panic recovery that reports a critical error via telemetry (with panic attribute, templateID, buildID) and returns a generic build error.
  • Server (internal/template/server/create_template.go): Replace panic log in background build with telemetry reporting and explicitly fail the build with a user-facing error.
• Telemetry:
  • Import and use otel/attribute and shared telemetry package for structured error reporting.

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