Enhance provider diagnostics visibility, change-case workflow UX, reports and docs

[DeepZone]

Motivation

• Surface the new RPKI/BGP provider and diagnostics data so operators can interpret multi-source disagreements, fallbacks and confidence when evaluating changes.
• Make Change Case preflight/post-change endpoints usable as an actual workflow and show decisions/actions in the UI.
• Expose watch webhook delivery results in a safe, non-secret way and provide operational docs for operators.

Description

• Extended API schemas to include ChangeCase workflow fields and WatchRun alert-delivery fields (ChangeCaseRead, WatchRunRead).
• Hardened POST /api/change-cases/{id}/run-preflight input handling for empty/whitespace lists and added guards for allowed decision/status values; kept existing endpoints and semantics.
• Added alert runtime config (retries/timeout) to system status without leaking secrets and trimmed error messages on delivery failures; webhook delivery recorded on WatchRun (alert_delivery_status, alert_delivered_at, alert_error_message).
• Enhanced report renderer templates (Markdown + HTML) to include RPKI provider, validation/fallback/disagreement, matched ROAs, BGP visibility source details, confidence score, conflicting origins, required actions and post-change verification status.
• Frontend: added Change Case workflow UI actions and status display (Run Case Preflight, Run Post-Change Verification, decision/risk/required actions/post-change status), report-level provider/decision summary, and Watch runs table includes alert delivery columns; corresponding API helpers were added to frontend/src/api.ts and types extended in frontend/src/types.ts.
• Added focused operational docs under docs/operations/ and an architecture note explaining provider modes and read-only model.
• Added/updated smoke tests verifying change-case preflight validation path and system status alert fields while preserving existing tests.

Testing

• Backend unit/integration test suite run: cd backend && pytest -q — result: 104 passed (no regressions in existing tests).
• Frontend production build run: cd frontend && npm run build — result: build succeeded (Vite production build completed).
• New/updated smoke tests included and executed as part of the backend run above; all passed.

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Codex Task