fix: update rack-proxy for security advisory (#16059)

Updates `rack-proxy` to a patched release so the `bundle-audit` step in
CI passes again. The refreshed advisory database flags the version in
our lockfile, which currently fails the `security-scan` job on every
open PR. `rack-proxy` is only used by the Vite dev server proxy, which
is mounted in development and local test runs, so the app's request
handling in production is not affected.

Fixes: GHSA-42qh-8mx8-7wqm

## How to reproduce

On `develop`, run:

```
bundle exec bundle-audit update
bundle exec bundle-audit check
```

It reports `rack-proxy 0.7.7` with the solution `upgrade to '>= 1.0.3'`
and exits with a non-zero status.

## What changed

- Updates `rack-proxy` from 0.7.7 to 1.0.3, the patched version named in
the advisory.
- Updates `vite_ruby` from 3.10.2 to 3.10.6. `rack-proxy` is a
transitive dependency of `vite_ruby`, and 3.10.2 pins it to `~> 0.6`.
Support for `rack-proxy` 1.0 landed in 3.10.5.
- Keeps `vite_ruby` on the 3.10 line on purpose. 3.11.0 detects the dev
server by reading a `tmp/vite-ruby.json` file written by a newer
`vite-plugin-ruby` than the 5.2.1 we use, so it needs to be taken
together with a JS dependency update.
- Only `Gemfile.lock` changes. No other gems are updated.

Gemfile.lock

@@ -700,8 +700,8 @@ GEM
       base64 (>= 0.1.0)
       logger (>= 1.6.0)
       rack (>= 3.0.0, < 4)
-    rack-proxy (0.7.7)
-      rack
+    rack-proxy (1.0.3)
+      rack (>= 2.0, < 4)
     rack-session (2.1.2)
       base64 (>= 0.1.0)
       rack (>= 3.0.0)
@@ -1015,11 +1015,11 @@ GEM
     vite_rails (3.10.0)
       railties (>= 5.1, < 9)
       vite_ruby (~> 3.0, >= 3.2.2)
-    vite_ruby (3.10.2)
+    vite_ruby (3.10.6)
       dry-cli (>= 0.7, < 2)
       logger (~> 1.6)
       mutex_m
-      rack-proxy (~> 0.6, >= 0.6.1)
+      rack-proxy (>= 0.6.1)
       zeitwerk (~> 2.2)
     warden (1.2.9)
       rack (>= 2.0.9)