Promote Conan package registry from Experiment to Beta
## Summary
Change the maturity status of the Conan package registry from **Experiment** to **Beta** to reflect the current state of development and readiness.
## Background
The Conan package registry has been in Experiment status since its introduction. With the completion of key features including:
- Conan v2 API support with recipe and package revisions
- Full revision workflow (upload, list, delete)
- Improved compatibility between Conan v1 and v2 clients
The registry is now stable enough to be promoted to Beta status.
### Documentation updates
Update the status badge and warning messages in the following documentation pages:
#### Conan 1 repository
- [ ] `doc/user/packages/conan_1_repository/_index.md`
- Change `Status: Experiment` to `Status: Beta`
- Update warning message about production readiness
#### Conan 2 repository
- [ ] `doc/user/packages/conan_2_repository/_index.md`
- Change `Status: Experiment` to `Status: Beta`
- Update warning message about production readiness
#### Supported functionality page
- [ ] `doc/user/packages/package_registry/supported_functionality.md`
- Update the "Supported package managers" table:
- Change Conan 1 from `[Experiment](...)` to `[Beta](...)`
- Change Conan 2 from `[Experiment](...)` to `[Beta](...)`
### Additional considerations
- [ ] Update any related API documentation if they contain maturity references:
- `doc/api/packages/conan_v1.md`
- `doc/api/packages/conan_v2.md`
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