Update Grafana Alloy to latest stable version

[noahwhite]

Story Summary

As a platform maintainer, I want to update Grafana Alloy to the latest stable version, so that metrics and logs forwarding remain compatible with Grafana Cloud and supported long term.

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✅ Acceptance Criteria

Define "done" in clear, testable terms (Given/When/Then if applicable).

• Latest alloy is rolled into a sysext
• Given Alloy is deployed, when it starts, then it reports the latest stable version.
• Given the updated version is running, when metrics and logs are emitted, then they appear in Grafana Cloud.
• No configuration warnings or runtime errors are present.
• Existing dashboards and alerts continue to function.

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📝 Additional Context

• Design:
• Docs:
• Related Issues/PRs:

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📦 Definition of Ready

• Acceptance criteria defined
• No unresolved external dependencies
• Story is estimated
• Team has necessary skills and access
• Priority is clear
• Business value understood

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✅ Definition of Done

• All acceptance criteria met
• Unit/integration tests written & passing
• Peer-reviewed
• Docs updated (if applicable)
• Verified in staging (if needed)
• No critical bugs/regressions

[linear]

GHO-21