chore(deps): bump aiohttp from 3.11.11 to 3.12.15 in /backend

---
updated-dependencies:
- dependency-name: aiohttp
  dependency-version: 3.12.15
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

backend/requirements.txt

@@ -9,7 +9,7 @@ passlib[bcrypt]==1.7.4
 cryptography
 
 requests==2.32.4
-aiohttp==3.11.11
+aiohttp==3.12.15
 async-timeout
 aiocache
 aiofiles