build(deps-dev): bump dotenv-rails from 2.7.6 to 3.0.0 in /backend

Bumps [dotenv-rails](https://github.com/bkeepers/dotenv) from 2.7.6 to 3.0.0.
- [Release notes](https://github.com/bkeepers/dotenv/releases)
- [Changelog](https://github.com/bkeepers/dotenv/blob/main/Changelog.md)
- [Commits](bkeepers/dotenv@v2.7.6...v3.0.0)

---
updated-dependencies:
- dependency-name: dotenv-rails
  dependency-type: direct:development
  update-type: version-update:semver-major
...

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

backend/Gemfile.lock

@@ -150,10 +150,10 @@ GEM
     digest-crc (0.6.4)
       rake (>= 12.0.0, < 14.0.0)
     docile (1.4.0)
-    dotenv (2.7.6)
-    dotenv-rails (2.7.6)
-      dotenv (= 2.7.6)
-      railties (>= 3.2)
+    dotenv (3.0.0)
+    dotenv-rails (3.0.0)
+      dotenv (= 3.0.0)
+      railties (>= 6.1)
     erubi (1.12.0)
     et-orbi (1.2.7)
       tzinfo
@@ -342,7 +342,7 @@ GEM
     mini_magick (4.11.0)
     mini_mime (1.1.2)
     mini_portile2 (2.8.5)
-    minitest (5.21.2)
+    minitest (5.22.2)
     msgpack (1.5.1)
     multi_json (1.15.0)
     multipart-post (2.1.1)
@@ -571,7 +571,7 @@ GEM
     websocket-extensions (0.1.5)
     xpath (3.2.0)
       nokogiri (~> 1.8)
-    zeitwerk (2.6.12)
+    zeitwerk (2.6.13)
 
 PLATFORMS
   ruby