fix(webapp): make prop-types a production dependency (#4492)

## Summary

The webapp's server bundle imports `prop-types` directly, but the
package was declared only as a `devDependency`. A production install
therefore leaves it out and the built server fails to boot:

```
Failed to start server: Error [ERR_MODULE_NOT_FOUND]: Cannot find package 'prop-types'
  imported from /triggerdotdev/apps/webapp/build/server/assets/server-build-*.js
```

Moving it to `dependencies` is the whole change.

## Why the bundle imports it

Nothing in the webapp's own code uses `prop-types` — there is no
reference to it, or to `PropTypes`, anywhere under `apps/webapp/app`. It
arrives through `recharts`, whose `react-smooth` dependency still
declares `propTypes` on its components.

That was invisible until recently. While `recharts` was resolved at
runtime, its `prop-types` import was satisfied inside `recharts`' own
dependency tree, which is production all the way down. #4486 added
`recharts` and `victory-vendor` to `ssr.noExternal` to fix a hydration
mismatch on every server-rendered chart; that inlines `react-smooth`
into the server bundle, which moves its `prop-types` import into the
webapp's own resolution scope — where the package was not available in
production.

So the bundling change was correct about *which* d3-shape build both
sides resolve, and wrong about what the production runtime would be able
to find.

## Verification

`docker/Dockerfile` builds the runtime dependencies with `pnpm install
--prod` against a `turbo prune --scope=webapp --docker` output, so I
reproduced exactly that: pruned the workspace, installed with `--prod`,
and imported `prop-types` from `apps/webapp`.

| | result |
| -- | -- |
| `main` as it stands (devDependency only) | `FAILS:
ERR_MODULE_NOT_FOUND` |
| with this change | `prop-types resolves OK` |

It resolves both as a CommonJS `require` and as an ESM `import`, which
is the form the bundle uses.

I also checked this is not one symptom of a wider problem: of the 169
bare specifier roots the server bundle imports, `prop-types` is the
**only** one that is a devDependency and not a production dependency.
The rest are node builtins or production dependencies.

The hydration fix from #4486 is unaffected — the rebuilt bundle still
carries the rounding d3-path build.

## Notes

`prop-types` is inert in production (its entry point swaps in
`factoryWithThrowingShims`), so this adds a 124 KB package that does no
work at runtime. It has to be resolvable regardless, because the import
is real.

An alternative would be adding `prop-types` to `ssr.noExternal` so it is
inlined and needs no runtime resolution. That keeps the dependency list
honest about the fact that the webapp itself does not use it, at the
cost of bundling a CommonJS package into the ESM server output. This
route is the smaller, better-understood change.

Worth following up separately: a check that every bare import in the
server bundle resolves from a production install would have caught this
before it landed. Local development installs every devDependency, so the
gap is invisible when the built server is run from a working tree.

Author: ericallam

apps/webapp/package.json

@@ -179,6 +179,7 @@
     "prism-react-renderer": "^2.3.1",
     "prismjs": "^1.30.0",
     "prom-client": "^15.1.0",
+    "prop-types": "^15.8.1",
     "qrcode.react": "^4.2.0",
     "random-words": "^2.0.0",
     "react": "^18.2.0",
@@ -260,7 +261,6 @@
     "npm-run-all": "^4.1.5",
     "postcss-import": "^16.0.1",
     "postcss-loader": "^8.1.1",
-    "prop-types": "^15.8.1",
     "rimraf": "^6.0.1",
     "style-loader": "^3.3.4",
     "supertest": "^7.0.0",