fix(stacks): same-origin RPC proxy so VPN/DNS/CORS can't break reads

[BreadrichEngels]

Problem

daopunk hit a CORS / access-control failure that only happened on a VPN (works with VPN off). CORS is enforced by the upstream server, so a VPN shouldn't normally trip it — the likely cause is the VPN's DNS/egress blocking or rerouting the public RPC endpoint, which the browser surfaces as a CORS/load failure.

Fix

Route the primary chain's reads through a first-party /api/rpc proxy. The browser only ever talks to the app's own origin (which already loaded fine), and the server forwards the JSON-RPC to the upstream — so a client-side DNS/CORS/ad-block filter can't break reads. Bonus: the upstream RPC URL stays off the client.

• New src/app/api/rpc/route.ts — same-origin JSON-RPC proxy (gnosis + sepolia; override upstreams via GNOSIS_RPC_URL / SEPOLIA_RPC_URL).
• web3.tsx — the gnosis transport uses the proxy only when NEXT_PUBLIC_APP_URL is set (absolute base so SSR prefetch works too); otherwise it's a plain http() — no behavior change if unconfigured.

Only affects reads/simulation (the wagmi transport). Tx submission still goes through Privy/the connector, untouched.

⚠️ Needs confirmation

I inferred the public RPC as the blocked endpoint but couldn't see the exact domain in daopunk's screenshot. @daopunk — what's the exact URL in the CORS error? If it's Supabase, WalletConnect, or something else, I'll extend the same-origin approach to that endpoint. To activate this: set NEXT_PUBLIC_APP_URL=https://stacks.bread.coop (and optionally private GNOSIS_RPC_URL) in the deploy env.

Test plan

• With NEXT_PUBLIC_APP_URL set, reads flow through /api/rpc (Network tab shows same-origin RPC calls); app works on a VPN.
• Unset NEXT_PUBLIC_APP_URL → behaves exactly as before.

🤖 Generated with Claude Code

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