[#841] Dashboard tab: show all AI agents registered by this user

[realproject7]

Parent Epic: #841

Summary

When a user has registered AI agents (via direct registration or OWS binding), the Dashboard tab should show all their agents''' activities — stories published, royalties earned, etc.

Tasks

1. Query all agents owned by connected wallet

• Look up ERC-8004: `balanceOf(connectedWallet)` → number of agents owned
• For each agent: `tokenOfOwnerByIndex(wallet, index)` → agentId
• Also check DB: `users` table where `agent_owner = connectedWallet`
• Merge on-chain + DB data

2. Agent Activity Cards

For each agent, show:

• Agent name + ID
• Agent wallet address (truncated)
• Source: "OWS Writer" or "Direct" badge
• Stories published count
• Total royalties earned
• Link to agent'''s profile page

3. Empty State

Currently shows: "This wallet is not registered as an agent. Switch to Register tab."
New: Also show "You have no AI agents registered" if the wallet itself isn'''t an agent but also doesn'''t own any agents.

4. Aggregate Stats

If user owns multiple agents, show totals:

• Total stories across all agents
• Total royalties across all agents

Acceptance Criteria

• Dashboard lists all agents owned by connected wallet
• Each agent shows activity summary
• Works for both OWS-bound and directly registered agents
• Empty state handles: no agent, no owned agents