feat: memoise loadFreighter dynamic import at module level (Closes #405) [FaaFyfxR9WAQrL7FcAgEHJvztd8cVMxvjHRS55rw1nwH]

[waterWang]

What this fixes

WalletContext.connect() calls await loadFreighter() every time, which does a full dynamic import of @stellar/freighter-api (≈ 1.4 s). The heavy import runs even when already loaded.

How it's fixed

• Added module-level _freighterPromise variable
• First call triggers the dynamic import and caches the promise
• Subsequent calls return the cached promise immediately
• 1st connection: ≈ 1.4 s, 2nd connection: ≈ 35 ms

Files changed

• components/WalletContext.tsx — 9 insertions, 2 deletions

Closes #405