fix: add Watch Mode create and edit forms

[DeepZone]

Motivation

• Watch Mode previously created a hard-coded placeholder target and lacked a usable create/edit UX, making the feature practically unusable.
• Provide a minimal UX hotfix so operators can create, edit and inspect watch targets with the full set of fields required by the API.

Description

• Reworked the Watch Mode UI by replacing the one-click hardcoded creation with a typed create form and an edit mode in frontend/src/components/WatchModeView.tsx that builds payloads via buildPayload and normalizes optional numeric fields.
• Added watch-type dependent inputs and defaults (interval_minutes = 60, is_active = true) and conditionally show fields for asn, prefix, bgp_visibility, and roa_preflight as requested.
• Implemented loading / submitting / error / success states, create (Create/Cancel) and edit (Save/Cancel) flows, delete confirmation, Run Now behavior, and refresh of the list and selected target after create/update/run/delete; expanded the runs history columns to include created_at, previous_status, status, changed, summary, and report_id.
• Enforced viewer-role read-only UX with a clear hint and hidden/disabled actions for viewer; updated RELEASE_NOTES.md with the v0.8.0-beta hotfix: Watch Mode UX section.

Testing

• Frontend build was executed with cd frontend && npm run build and completed successfully (vite build output shown).
• Backend was not changed for this hotfix and therefore no backend tests were required.
• No database migrations were added.

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Codex Task