feat(gui): add discovery triage, network scan management, and approval workflow pages (M24)

Three new GUI surfaces closing the backend-to-frontend gap for V2:

- Discovery triage page: summary stats bar, DataTable with claim/dismiss
  actions, status/agent filters, collapsible scan history panel
- Network scan target management: CRUD with create modal, enable/disable
  toggle, Scan Now button, last scan results display
- Jobs page approval workflow: Approve/Reject buttons for AwaitingApproval
  jobs, rejection reason modal, pending approval banner with count,
  AwaitingApproval/AwaitingCSR added to status filter dropdown

Also adds 13 new frontend tests, 4 API types, 12 API client functions,
2 sidebar nav items, 2 routes, and discovery status badge styles.

Docs updated: README, architecture, quickstart, demo-advanced, CLAUDE.md,
roadmap. Version bumped to v2.0.4.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

docs/quickstart.md

@@ -89,7 +89,7 @@ The dashboard comes pre-loaded with 15 demo certificates across multiple teams,
 
 The main dashboard shows total certificates, how many are expiring soon, how many have expired, the renewal success rate, and four charts: an **expiration heatmap** (90-day weekly buckets), **renewal success rate trends** (30-day line chart), **certificate status distribution** (donut chart), and **issuance rate** (30-day bar chart).
 
-Explore the sidebar: Certificates, Agents, Policies, Jobs, Audit Trail, Notifications, Profiles, Teams, Owners, Agent Groups, Fleet Overview, Short-Lived Credentials, Discovery.
+Explore the sidebar: Certificates, Agents, Policies, Jobs, Audit Trail, Notifications, Profiles, Teams, Owners, Agent Groups, Fleet Overview, Short-Lived Credentials, Discovery, and Network Scans.
 
 ### Scenarios to walk through