fix(web): load the inlang plugin from node_modules, not a CDN

`web/project.inlang/settings.json` pointed `modules` at
https://cdn.jsdelivr.net/npm/@inlang/plugin-message-format@4/dist/index.js —
inlang's stock `paraglide-js init` scaffolding, which nobody had a reason to
keep. It made `bun run codegen` need the network at build time, so in a
sandbox that has none (the Nix build; any air-gapped CI) the plugin import
failed and paraglide compiled ZERO messages.

That failure is silent by design: the inlang SDK logs a PluginImportError as a
WARNING, paraglide still prints "Successfully compiled" and exits 0, vite
bundles the empty message set, and the console only dies at request time inside
renderToReadableStream because every `m.foo()` is undefined. Reported from a
NixOS host running punktfunk-web-server.

The plugin is a normal npm package, so depend on it like one: add
@inlang/plugin-message-format as a devDependency and reference it by relative
path. `loadProjectFromDirectory` (which both `paraglide-js compile` and the
vite plugin use) imports non-`http` modules straight off disk, and the shipped
dist/index.js is a self-contained bundle with no imports of its own, so it
loads from the data: URL exactly as the CDN copy did. Compiles 268 messages
offline, with no project.inlang/cache round-trip.

Add tools/check-i18n.mjs, run at the end of `codegen`, so this can never ship
silently again: it fails the build on a remote `modules` entry, a module that
does not resolve, or a compiled message count below what messages/en.json
defines. Verified it catches all three (remote URL, missing plugin, corrupt
plugin that compiles to 0 messages) and passes a healthy build.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

web/bun.lock

@@ -25,6 +25,7 @@
       "devDependencies": {
         "@biomejs/biome": "^2.5.2",
         "@inlang/paraglide-js": "^2.20.2",
+        "@inlang/plugin-message-format": "^4.4.0",
         "@storybook/react-vite": "^10.4.6",
         "@tailwindcss/vite": "^4.3.2",
         "@tanstack/nitro-v2-vite-plugin": "^1.155.0",
@@ -283,6 +284,8 @@
 
     "@inlang/paraglide-js": ["@inlang/paraglide-js@2.20.2", "", { "dependencies": { "@inlang/recommend-sherlock": "^0.2.1", "@inlang/sdk": "^2.10.0", "commander": "11.1.0", "consola": "3.4.0", "json5": "2.2.3", "unplugin": "^2.1.2", "urlpattern-polyfill": "^10.0.0" }, "peerDependencies": { "typescript": ">=5.6" }, "optionalPeers": ["typescript"], "bin": { "paraglide-js": "bin/run.js" } }, "sha512-V8iY3uu/vQU94gEag1bdC3glMJSp4Dg3XMwfnabZLBh1Dv0F++DvDYlMeniqv2+nHbnS/twB75AM140OmpHDEg=="],
 
+    "@inlang/plugin-message-format": ["@inlang/plugin-message-format@4.4.0", "", { "dependencies": { "flat": "^6.0.1" } }, "sha512-n4aXt6XVg5kxhKoLAhi9nMgZtCA9iS0QOaXte56VqxWHcfj9O4c4gOkyVQZH7H9D8h7OZufCrO1sZGYOypPwEA=="],
+
     "@inlang/recommend-sherlock": ["@inlang/recommend-sherlock@0.2.1", "", { "dependencies": { "comment-json": "^4.2.3" } }, "sha512-ckv8HvHy/iTqaVAEKrr+gnl+p3XFNwe5D2+6w6wJk2ORV2XkcRkKOJ/XsTUJbPSiyi4PI+p+T3bqbmNx/rDUlg=="],
 
     "@inlang/sdk": ["@inlang/sdk@2.10.2", "", { "dependencies": { "@lix-js/sdk": "0.4.10", "@sinclair/typebox": "^0.31.17", "kysely": "^0.28.12", "sqlite-wasm-kysely": "0.3.0", "uuid": "^14.0.0" } }, "sha512-O1ki72SNK6LPagaGrvlioBb1mWKvump7cO7P85hfGZjdFTmDdn3icI0A6MvaBsB3P9KQHAjzyubnN1OslGufTw=="],
@@ -1383,6 +1386,8 @@
 
     "find-up": ["find-up@8.0.0", "", { "dependencies": { "locate-path": "^8.0.0", "unicorn-magic": "^0.3.0" } }, "sha512-JGG8pvDi2C+JxidYdIwQDyS/CgcrIdh18cvgxcBge3wSHRQOrooMD3GlFBcmMJAN9M42SAZjDp5zv1dglJjwww=="],
 
+    "flat": ["flat@6.0.1", "", { "bin": { "flat": "cli.js" } }, "sha512-/3FfIa8mbrg3xE7+wAhWeV+bd7L2Mof+xtZb5dRDKZ+wDvYJK4WDYeIOuOhre5Yv5aQObZrlbRmk3RTSiuQBtw=="],
+
     "focus-trap": ["focus-trap@7.5.4", "", { "dependencies": { "tabbable": "^6.2.0" } }, "sha512-N7kHdlgsO/v+iD/dMoJKtsSqs5Dz/dXZVebRgJw23LDk+jMi/974zyiOYDziY2JPp8xivq9BmUGwIJMiuSBi7w=="],
 
     "foreground-child": ["foreground-child@3.3.1", "", { "dependencies": { "cross-spawn": "^7.0.6", "signal-exit": "^4.0.1" } }, "sha512-gIXjKqtFuWEgzFRJA9WCQeSJLZDjgJUOMCMzxtvFq/37KojM1BFGufqsCy0r4qSQmYLsZYMeyRqzIWOMup03sw=="],