fix(build): do not run the Sentry release upload as a root postbuild hook

[Chirag6722]

Fixes #1444.

The root package.json had:

"build": "turbo run build",
"sentry:sourcemaps": "... sentry-cli releases new ... sentry-cli sourcemaps upload ... dist",
"postbuild": "bun run sentry:sourcemaps"

so every bun run build — local or CI — chained a Sentry release creation and sourcemap upload onto the build. That needs deploy-only credentials to succeed, and it targets a root dist/ that the Turbo build doesn't produce (apps/web emits .next).

Change

Remove the root postbuild hook. Nothing else moves:

• sentry:sourcemaps stays at the root as an explicit, manually-invocable command.
• The real release path is untouched — apps/web already carries its own identical sentry:sourcemaps plus "postdeploy": "bun run sentry:sourcemaps", which fires on deploy, after the app build, which is where it belongs.

That last point is why this is a safe deletion rather than a behaviour change: the root hook was a duplicate of the web app's, firing at build time instead of deploy time.

Acceptance criteria

• bun run build succeeds without SENTRY_AUTH_TOKEN — verified: 7 successful, 7 total, exit 0, with no Sentry configuration present.
• No Sentry release/upload attempted during ordinary builds — verified: no sentry-cli invocation in the build output. (The [@sentry/nextjs] deprecation warnings that remain come from the Next.js build plugin, not the CLI upload.)
• Production deployment still creates the release — unchanged; it runs from apps/web's postdeploy.

I did not run the pre-change build to demonstrate the failure, because with credentials present that command creates a real release in the supermemory org — not something to trigger from a contributor's machine.

Left alone

#1444 also suggests correcting the dist path / --strip-prefix and replacing the POSIX _SENTRY_RELEASE=$(...) syntax with something cross-platform. Both apply to the apps/web deploy command and depend on how your deploy pipeline is wired, which I can't see from here — so this PR sticks to removing the hook. Happy to follow up on either if you say what the deployed output layout is.