fix(deps): revert OT 1.41/azure-ai-projects 2.1 due to upstream pins

Resolves pip ResolutionImpossible errors in lint, backend_tests, and
docker-build jobs:

- semantic-kernel 1.41.3 requires azure-ai-projects~=1.0.0b12 (cannot use 2.1.0)
- azure-monitor-opentelemetry 1.8.7 pins opentelemetry-sdk==1.40 (cannot use 1.41.1)

Reverted to versions compatible with both umbrella packages. The 2.1.0
azure-ai-projects pin in dependabotchanges was incompatible with the
semantic-kernel version present in the repo and was previously masked
because CI didn't run on that branch.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Copilot

src/backend/requirements.txt

@@ -45,10 +45,10 @@ aiortc
 opentelemetry-exporter-otlp-proto-grpc
 opentelemetry-exporter-otlp-proto-http
 azure-monitor-events-extension
-opentelemetry-sdk==1.41.1
-opentelemetry-api==1.41.1
-opentelemetry-semantic-conventions==0.62b1
-opentelemetry-instrumentation==0.62b1
-opentelemetry-instrumentation-fastapi==0.62b1
+opentelemetry-sdk==1.40.0
+opentelemetry-api==1.40.0
+opentelemetry-semantic-conventions==0.61b0
+opentelemetry-instrumentation==0.61b0
+opentelemetry-instrumentation-fastapi==0.61b0
 azure-monitor-opentelemetry==1.8.7
-azure-ai-projects==2.1.0
+azure-ai-projects==1.0.0b12