deps(python): bump sse-starlette from 2.2.1 to 3.2.0 in /backend

[dependabot]

Bumps sse-starlette from 2.2.1 to 3.2.0.

Release notes

Sourced from sse-starlette's releases.

v3.2.0

What's Changed

• [feat] Allow disabling automatic draining immediately on sigterm by @​yuliy-openai in sysid/sse-starlette#157
• feat: add enable_automatic_graceful_drain_mode() for re-enabling auto… by @​sysid in sysid/sse-starlette#158

New Contributors

• @​yuliy-openai made their first contribution in sysid/sse-starlette#157

Full Changelog: sysid/sse-starlette@v3.1.2...v3.2.0

v3.1.2

What's Changed

• fix: prevent watcher task leak by using threading.local (#152) by @​sysid in sysid/sse-starlette#153

Full Changelog: sysid/sse-starlette@v3.1.1...v3.1.2

v3.1.1

What's Changed

• fix(shutdown): detect uvicorn shutdown via signal handler introspection by @​sysid in sysid/sse-starlette#151

Full Changelog: sysid/sse-starlette@v3.1.0...v3.1.1

v3.1.0

What's Changed

• chore(deps): bump actions/setup-python from 3 to 6 by @​dependabot[bot] in sysid/sse-starlette#143
• Fix Issue #149: handle_exit cannot signal context-local events by @​sysid in sysid/sse-starlette#150

Full Changelog: sysid/sse-starlette@v3.0.4...v3.1.0

v3.0.4

What's Changed

• Add starlette to dependencies by @​WOnder93 in sysid/sse-starlette#147
• Maintenance: CI updates, Python 3.13 support, and packaging fixes by @​sysid in sysid/sse-starlette#148

New Contributors

• @​WOnder93 made their first contribution in sysid/sse-starlette#147

Full Changelog: sysid/sse-starlette@v3.0.3...v3.0.4

v3.0.3

What's Changed

• Security: Upgrade Starlette to 0.49.1 to address CVE-2025-62727 by @​ColeMurray in sysid/sse-starlette#144

New Contributors

• @​ColeMurray made their first contribution in sysid/sse-starlette#144

Full Changelog: sysid/sse-starlette@v3.0.2...v3.0.3

... (truncated)

Commits

• 9101a42 Bump version to 3.2.0
• c3248fc Merge pull request #158 from sysid/pr-157
• c99dd67 Merge pull request #157 from yuliy-openai/optional_auto_drain
• ed35777 feat: add enable_automatic_graceful_drain_mode() for re-enabling auto-drain
• 15f26cb [feat] Allow disabling automatic draining immediately on sigterm
• fc50af6 chore: update gitignore
• 268b3cd feat: add pre-commit hooks for format, lint, and mypy
• 618ac0e Bump version to 3.1.2
• 6d68ba9 Merge pull request #153 from sysid/fix/152_shutdown_watcher_leak
• 89faa04 fix: prevent watcher task leak with threading.local (#152)
• Additional commits viewable in compare view

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Summary by cubic

Upgrade sse-starlette from 2.2.1 to 3.2.0 to improve SSE stability and shutdown behavior. Includes fixes for watcher task leaks and better SIGTERM handling.

• Dependencies

  • sse-starlette: 2.2.1 → 3.2.0 (backend). Starlette remains pinned at 0.49.1.

• Migration

  • No code changes expected.
  • Verify SSE connections close cleanly on server shutdown. If you customize drain behavior, new APIs allow disabling or re-enabling automatic graceful drain.

^{Written for commit e5e71ff. Summary will update on new commits.}

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Quality Gate passed

Issues
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[cubic-dev-ai]

No issues found across 2 files