feat: rework new opportunity page to match profile edit layout

[nadavosa]

Summary

• Replaces the simple card form with the same PageContainer + SectionCard layout used by the opportunity profile page
• Title is presented in a Wrench section card (same as Opportunity Details on the profile)
• Contact details are in a ChatsCircle section card, always in edit mode, pre-filled from the current agent's representative
• Validation uses zod + react-hook-form with the same phone regex and email rules as opportunityContactDetailsSchema
• Save POSTs { title, contact: { name, phone, email }, agentId } to POST /api/opportunity/ and redirects to the new opportunity's profile on success

Closes #445

Test plan

• Log in as an agent; click "New Opportunity" from the dashboard
• Verify the page uses the profile-style section card layout (not the old card form)
• Verify contact name/phone/email are pre-filled from the logged-in agent's representative
• Verify title is empty and required; submit without it shows validation error
• Verify phone/email validation works the same as on the opportunity profile contact section
• Fill in all fields and submit; confirm redirect to the new opportunity's profile page

🤖 Generated with Claude Code

[nadavosa]

Review

Overall the approach is solid — three-form aggregation, profile-style layout, role-aware home page, correct SDK upgrade path. A few things worth addressing before merge:

Issues:

1. AccompanyingDetailsEdit no-op handlers (NewOpportunity.tsx ~line 823): onCancel={() => {}} and onSubmit={() => {}} mean the Cancel and Submit buttons inside that component render and are clickable but do nothing. The agent will click them expecting something to happen. Either suppress those buttons (if AccompanyingDetailsEdit supports that) or document that submission is driven by the outer Create button only.

2. Empty state missing in AgentOpportunityCards: When opportunities is an empty array (a freshly registered agent with no opportunities yet), the component renders nothing — no message. Add a simple empty-state string so the home page isn't just a button with a blank area below it.

3. category / category_id sent as "" (buildCreatePayload): These are required fields in OpportunityFormDataWithAgentSubmitter and we're sending empty strings. If the BE rejects blank values here a creation attempt will silently fail. Worth confirming with BE what the correct sentinel is (null? omit entirely? a real default?).

Minor notes:

• keyToLabel / labelToKey maps are rebuilt on every render in the component body — should be useMemo(() => ..., [apiLanguages]) since they only change when apiLanguages changes.
• opportunity_type: isAccompanying ? "accompanying" : "volunteering" — events map to "volunteering". The SDK type only has two values so this is correct, but it's worth a short comment that the BE distinguishes events from regular via onetime_date_time.
• useGetCurrentAgent in AgentOpportunityCards fires two requests (/me → /agent/{id}) when we only need the agentId from /me. Not a blocker but a minor over-fetch.