Bump blinker from 1.8.2 to 1.9.0 in /backend/src

Bumps [blinker](https://github.com/pallets-eco/blinker) from 1.8.2 to 1.9.0.
- [Release notes](https://github.com/pallets-eco/blinker/releases)
- [Changelog](https://github.com/pallets-eco/blinker/blob/main/CHANGES.rst)
- [Commits](pallets-eco/blinker@1.8.2...1.9.0)

---
updated-dependencies:
- dependency-name: blinker
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

backend/src/requirements.txt

@@ -1,4 +1,4 @@
-blinker==1.8.2
+blinker==1.9.0
 click==8.1.7
 Flask==3.0.3
 itsdangerous==2.2.0