feat: Add silence annotation to web UI

[TheMeier]

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Which user-facing changes does this PR introduce?

[FEATURE] UI: Add support for silence annotations

[Copilot]

Pull request overview

This PR adds support for displaying and managing silence annotations in the Alertmanager web UI. Annotations are optional key-value pairs that can be attached to silences for additional context. The implementation adds annotation input fields to the silence creation/edit form and displays annotations in both the silence detail view and silence list view.

Changes:

• Added annotation input field with validation in the silence form
• Added annotation display in silence detail and list views
• Implemented parsing and validation logic for annotation key-value pairs

Reviewed changes

Copilot reviewed 5 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
ui/app/src/Views/SilenceView/Views.elm	Displays annotations in the silence detail view with inline matchers styling
ui/app/src/Views/SilenceList/SilenceView.elm	Displays annotations in the silence list view and adds "Matchers:" label for consistency
ui/app/src/Views/SilenceForm/Views.elm	Adds annotation input UI with add/delete buttons and validation feedback
ui/app/src/Views/SilenceForm/Updates.elm	Implements annotation add/delete/update logic and form validation
ui/app/src/Views/SilenceForm/Types.elm	Adds annotation data structures, parsing, and validation functions

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 8 changed files in this pull request and generated 2 comments.

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[Spaceman1701]

Not really a code review of the Elm, but I ran this patch locally and the UI seemed good to me.

It might be nice if the annotations box didn't let you add duplicate annotations, but otherwise it seems fine.

[Copilot]

Pull request overview

Copilot reviewed 7 out of 8 changed files in this pull request and generated 3 comments.

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