fix(work-item): separate work order and invoice actions, remove duplicate buttons

[Dev869]

Summary

Surgical UI cleanup of web/src/routes/contractor/WorkItemDetail.tsx so WORK ORDER actions and INVOICE actions are clearly separated and de-duplicated. No data-model changes. Quotes route untouched.

What was duplicated / removed

• Duplicate full-width "Send to Client →" button (mailto fallback): removed. The Email compose card already covers sending the work order. The now-dead handleSendToClient function and its now-unused httpsCallable / functions imports were also removed.
• Duplicate "Approve & Generate PDF" button: it was rendered twice in the actions row (identical onClick, only layout classes differed). Removed the redundant one; it now appears exactly once.
• Duplicate "Invoice Status Actions" block (Mark as Paid / Mark Overdue): removed. These transitions already exist in the Invoice Status card.

What was separated / relabeled

• Invoice Tracking card header: "Invoice" → "Invoice Status" (status display only).
• Email compose grid: now its own clearly-labeled "Email" section (Work Order composer + Invoice composer), separate from the Invoice Status card.
• Remaining work-order-only actions (View PDF + Send Work Order to Client) grouped under a new visually-distinct "Work Order Actions" card placed after the Email compose grid.
• Primary actions row relabeled "Primary Actions" (Discard | Save | Approve & Generate PDF once | Complete).

No restyling — only reorganization and de-duplication. All conditional/status gating logic and styling tokens preserved.

Test plan

• cd web && npx tsc -b — exit 0
• npx eslint src/routes/contractor/WorkItemDetail.tsx — clean (exit 0)
• npx vitest run — 59/59 pass
• Manual: verify no duplicate buttons; work-order vs invoice actions visually grouped across draft/sent/paid/overdue/approved/completed states

🤖 Generated with Claude Code

[github-actions]

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