feat: agent can publish an opportunity within the app

[nadavosa]

Sub-issue of #675.

Context

The opportunity creation form at /dashboard/opportunities/new exists but is broken in two ways:

1. Contact fields (name, email, phone) never pre-populate because GET /agent/me does not exist on the BE yet (feat: include agentId in GET /user/me response be#684). The useGetCurrentAgent() hook always returns undefined.

2. The form submission crashes — POST /api/opportunity/ does not exist on the BE. The only opportunity creation route is the public legacy form. A dashboard-specific endpoint needs to be added on the BE side.

Blocked on

• feat: include agentId in GET /user/me response be#684 — GET /agent/me (pre-fill)
• BE issue to be opened — POST /opportunity/ dashboard endpoint (developer must check network tab, confirm the failing request, and open the BE issue)

Fix

Pre-fill (src/components/Dashboard/NewOpportunity/NewOpportunity.tsx):

• Once BE feat: Opportunities table, green "matched" indicator and matched volunteer name #684 is merged, verify the useEffect pre-fill (lines 49-55) populates contactName, contactEmail, contactPhone correctly
• Add a loading skeleton while agentLoading is true
• Add a clear error state if agent is null after loading

Submit crash:

• Reproduce as an NGO user: open the page, fill the form, submit, check the network tab
• Identify the exact failing endpoint
• BE issue 236 for the missing POST /opportunity/ dashboard route
• Once the BE endpoint exists, wire it up and verify end-to-end

After successful submit:

• Verify redirect to the new opportunity profile page works
• Verify the NGO can see and edit their opportunity at /dashboard/opportunities/:id

[thnndnly]

@nadavosa re "BE issue to be opened — POST /opportunity/ dashboard endpoint": that issue already exists as need4deed-org/be#236 (still an empty placeholder), so no need to open a new one, it just needs a spec.

Confirmed the failing endpoint: submitting the form sends POST /api/opportunity/ and gets 404 Not Found (no handler on the BE; the only create route is the public /opportunity/legacy). Request payload: { title, contact: { name, email, phone }, agentId }.