chore(deps): bump fastapi from 0.115.12 to 0.136.1 in /backend

Bumps [fastapi](https://github.com/fastapi/fastapi) from 0.115.12 to 0.136.1.
- [Release notes](https://github.com/fastapi/fastapi/releases)
- [Commits](https://github.com/fastapi/fastapi/compare/0.115.12...0.136.1)

---
updated-dependencies:
- dependency-name: fastapi
  dependency-version: 0.136.1
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

backend/pyproject.toml

@@ -15,7 +15,7 @@ dependencies = [
     "cachetools==5.5.2",
     "cloudscraper==1.2.71",
     "cryptography>=41.0.0",
-    "fastapi==0.115.12",
+    "fastapi==0.136.1",
     "feedparser==6.0.10",
     "httpx==0.28.1",
     "playwright==1.59.0",