Implement multi-pool dashboard view — aggregate credits, total stake, and APY across all user positions

[prodbycorne]

Problem

The farm page renders each pool position as an independent row with no summary. A user farming across three pools must mentally add up their credits and stakes. There is no at-a-glance view of total portfolio value or portfolio-level daily rate.

useAllUserPositions is already defined in useSorobanQuery.ts and fetches all positions in parallel, but the farm page never shows aggregated values from this hook.

Acceptance Criteria

• A <FarmSummaryBar> component renders above the pool rows showing:
  • Total Stake across all pools (sum of lockedAmount converted to XLM equivalent for display)
  • Total Credits Earned (sum of live-ticking credit values from useLiveCredits per pool)
  • Portfolio Daily Rate (sum of per-pool dailyRate × lockedAmount)
  • Estimated APY — formula: (totalDailyRate / totalStake) × 365 × 100 formatted as a percentage
• APY is marked with an asterisk and a tooltip: "Estimated based on current rates. Subject to change as TVL fluctuates."
• The summary bar is hidden when useAllUserPositions returns all zero-stake positions
• The summary bar's credit counter also live-ticks using the aggregate of all per-pool useLiveCredits values
• A Vitest snapshot test renders <FarmSummaryBar> with two mock positions and verifies the aggregated values in the output

Relevant Files

• src/hooks/useSorobanQuery.ts — useAllUserPositions (exists)
• src/app/farm/page.tsx — render <FarmSummaryBar> above pool rows
• src/components/FarmSummaryBar/FarmSummaryBar.tsx — create
• src/hooks/useLiveCredits.ts — depends on issue Implement real-time credit accrual ticker in farm rows without polling the contract #23

[Oluwasuyi-Timilehin]

Hello maintainers I'm a full stack developer experience in building scalable systems I can handle this perfectly if assigned

[grantfox-oss]

🦊 GrantFox — @Oluwasuyi-Timilehin has been assigned to this issue as part of the Official Campaign campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #43)
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