Update Client Dashboard to show listings section (/client)

[johneliud]

Description

Update the existing Client Dashboard at /client to include a listings section alongside the existing on-chain projects grid.

Changes

• Add "My Listings" section above the existing "Active Projects" section
• Each listing card shows: title, status badge (Open / Filled), application count, "Review Applications" link to /client/listings/[id]/applications
• Add "Post a Listing" button in the page header (alongside the existing "New Project" button)
• Fetch client listings via getClientListings(clientAddress) from lib/listings.ts

Acceptance Criteria

• Listings section appears when wallet is connected
• Application count updates accurately
• "Post a Listing" links to /client/listings/new
• "New Project" (direct creation) is preserved and still functional
• Empty listings state handled gracefully