Bump litellm from 1.37.7 to 1.94.0.dev2 in /backend/requirements

[dependabot]

Bumps litellm from 1.37.7 to 1.94.0.dev2.

Release notes

Sourced from litellm's releases.

v1.90.5

Verify Docker Image Signature

All LiteLLM Docker images are signed with cosign. Every release is signed with the same key introduced in commit 0112e53.

Verify using the pinned commit hash (recommended):

A commit hash is cryptographically immutable, so this is the strongest way to ensure you are using the original signing key:

cosign verify \
  --key https://raw.githubusercontent.com/BerriAI/litellm/0112e53046018d726492c814b3644b7d376029d0/cosign.pub \
  ghcr.io/berriai/litellm:v1.90.5

Verify using the release tag (convenience):

Tags are protected in this repository and resolve to the same key. This option is easier to read but relies on tag protection rules:

cosign verify \
  --key https://raw.githubusercontent.com/BerriAI/litellm/v1.90.5/cosign.pub \
  ghcr.io/berriai/litellm:v1.90.5

Expected output:

The following checks were performed on each of these signatures:
  - The cosign claims were validated
  - The signatures were verified against the specified public key

---

What's Changed

• chore(release): backport #33592 to stable/1.90.x and cut 1.90.5 by @​yuneng-berri in BerriAI/litellm#33610

Full Changelog: BerriAI/litellm@v1.90.4...v1.90.5

v1.93.0-rc.2

Verify Docker Image Signature

All LiteLLM Docker images are signed with cosign. Every release is signed with the same key introduced in commit 0112e53.

Verify using the pinned commit hash (recommended):

A commit hash is cryptographically immutable, so this is the strongest way to ensure you are using the original signing key:

</tr></table> 

... (truncated)

Commits

• 229159c Merge pull request #33491 from BerriAI/litellm_internal_staging
• 906897b Merge pull request #33473 from BerriAI/litellm_claude_code_passthrough
• 39c01fe Merge pull request #33482 from BerriAI/litellm_/laughing-herschel-d4f735
• 3cea243 fix(key management): enforce minimum custom key length and mask short keys in...
• c4fee0e test(e2e/claude_code): retry rate-limit-shaped CLI failures with backoff
• 63e0be6 Merge remote-tracking branch 'origin/litellm_internal_staging' into litellm_/...
• 614dd87 Merge pull request #33446 from BerriAI/litellm_/chat-ui-first-message-bug-4ca43c
• fac43df fix(complexity_router): return empty dict from _classifier_call_metadata when...
• 7b7bec1 Merge pull request #33484 from BerriAI/litellm_/ddtrace-security-regression-3...
• 585f21a chore(ui): remove Hide Usage Indicator flag and hook
• Additional commits viewable in compare view

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