feat: add Express 5 adapter

[bogdantarasenko]

Summary

Adds a community Express 5 adapter under @supabase/server/adapters/express, alongside the existing Hono, H3, and Elysia adapters.

• withSupabase(config) returns a standard Express middleware. Resolved context lives on res.locals.supabaseContext via Express.Locals declaration merging, so downstream handlers and middleware get full type inference.
• requireAuth(...modes) is a per-route guard that asserts the context is set and (optionally) that authMode matches one of the listed modes. Useful when one app mixes routes with different auth requirements.
• withSupabaseRoute(config, handler) is a per-route wrapper for cases where global middleware doesn't fit — same context shape, async errors are forwarded to next().
• Auth errors flow through a configurable onError option. Default is next(error) (Express-idiomatic); pass a function to send a custom response instead.
• The Express req → Fetch Request bridge preserves headers (incl. multi-value Set-Cookie / Cookie), composes absolute URLs under app.set('trust proxy', true), and forwards bodies for non-GET/HEAD methods.

express is added as an optional peer dep (^5.0.0), so users who don't import the adapter aren't forced to install Express. No new runtime dependencies.

What's in the diff

• src/adapters/express/{middleware,require-auth,with-supabase-route,to-fetch-request,index}.ts — adapter source
• src/adapters/express/*.test.ts — unit tests covering every AuthMode (user / publishable / secret / none), the array form, invalid-JWT / missing-credential failures, the res.locals.supabaseContext short-circuit path, default and custom onError, the requireAuth() guard (present / missing context / mode mismatch), the withSupabaseRoute() wrapper (success, auth failure, async-thrown errors), and the req → Request bridge (headers, body, trust-proxy URL composition)
• tsdown.config.ts, package.json exports + peerDependencies + peerDependenciesMeta + devDependencies, jsr.json — wire the new entry point
• README.md, src/adapters/README.md, new docs/adapters/express.md — documentation

Test plan

• pnpm install resolves the new peer/dev dependencies
• pnpm typecheck
• pnpm lint
• pnpm test — 190/190 pass, including all Express adapter test files
• pnpm build produces dist/adapters/express/index.{mjs,cjs,d.mts,d.cts}
• Reviewer: confirm the optional-peer-dep approach (peerDependenciesMeta) is consistent with the other adapters
• Reviewer: smoke-test on an Express 5 app with app.set('trust proxy', true) behind a reverse proxy to confirm the bridged URL uses X-Forwarded-*

[kallebysantos]

Please remove this .chief/ folder, I believe it was accidentally added