Implement Sentry release creation

[RasputinKaiser]

Summary

• replace the Sentry observability stub with real Sentry REST API release creation
• create optional deploy records when the release includes an environment
• surface Sentry API errors and keep setup guidance aligned with the release API scopes

Duplicate check

• checked existing open/closed PRs for "sentry" and "observability-sentry" before submitting; none found
• checked I need PRs submitted for each platform listed in readme #6 comments; Sentry is only covered by the broad observability stub bucket, not an existing adapter PR

Tests

• corepack pnpm test -- packages/observability/sentry/src/index.test.ts
• corepack pnpm --filter @profullstack/sh1pt-observability-sentry typecheck
• corepack pnpm --filter @profullstack/sh1pt-observability-sentry build
• git diff --check

Relates to #6