Embedded the frontend in the binary, and built it in the build script

`npm run sync` in web/ copies the build output (web/dist, from npm run build)
to internal/frontend/dist, which the binary embeds. Go can't embed from
outside the package's directory (web/ is also outside the Go module), hence
the copy. Only dist/.gitkeep is committed, so a fresh clone still compiles,
and a binary built without syncing first serves no frontend.

job-search serve serves server.frontend.dir if it is set, or else the
embedded build, or warns that there is no frontend. scripts/build.sh builds
and syncs the frontend before building, running npm ci first for a release
or when web/node_modules is missing.

web/CODE_CONVENTIONS.md

@@ -15,7 +15,8 @@ npm run lint           # eslint .
 npm run format:check   # prettier --check .
 npm run format         # prettier --write .: formats every file
 npm run generate:api   # regenerate src/types/api.ts from the backend's OpenAPI description
-npm run build          # typecheck, then vite build
+npm run build          # typecheck, then vite build into dist/
+npm run sync           # copy dist/ to ../internal/frontend/dist/, which the backend embeds
 npm run dev            # dev server; /api and /ws go to the backend (API_PROXY_TARGET, default localhost:9393)
 ```
 
@@ -79,7 +80,7 @@ if (isRelease(parsed)) { ... }
 | `src/primitives/` | Solid primitives: state and loading, no markup (`createX.ts`)                                      |
 | `src/components/` | Components, one exported component per file                                                        |
 | `src/lib/`        | Plain functions: no Solid, no DOM where avoidable                                                  |
-| `scripts/`        | Development scripts run by npm, in TypeScript (`generateApiTypes.ts`)                              |
+| `scripts/`        | Development scripts run by npm, in TypeScript (`generateApiTypes.ts`, `syncDist.ts`)               |
 
 - Components' files are PascalCase, named after the component
   (`MarkMenu.tsx`). Other files are usually camelCase (`format.ts`); the

web/README.md

@@ -14,6 +14,10 @@ default address (`http://localhost:9393`). To use another, copy `.env.example`
 to `.env` and set `API_PROXY_TARGET`. `VITE_API_BASE_URL` changes the `/api`
 prefix for production builds.
 
+`npm run build` type-checks and builds the app into `dist/`. `npm run sync`
+then copies `dist/` to `../internal/frontend/dist/`, where the backend embeds
+it: the next Go build of `job-search` serves it. The copy isn't committed.
+
 Before committing, `npm run check` type-checks, lints (ESLint) and checks
 formatting (Prettier); `npm run format` formats everything. See
 [CODE_CONVENTIONS.md](CODE_CONVENTIONS.md).

web/package.json

@@ -12,7 +12,8 @@
     "format": "prettier --write .",
     "format:check": "prettier --check .",
     "check": "npm run typecheck && npm run lint && npm run format:check",
-    "generate:api": "node scripts/generateApiTypes.ts"
+    "generate:api": "node scripts/generateApiTypes.ts",
+    "sync": "node scripts/syncDist.ts"
   },
   "dependencies": {
     "solid-js": "^1.9.3"

web/scripts/syncDist.ts

@@ -0,0 +1,24 @@
+// Copies the frontend's build output, dist/ (from npm run build), to
+// ../internal/frontend/dist/, which the backend embeds, so the next Go build
+// of job-search serves this frontend:
+//
+//   npm run build && npm run sync
+//
+// The old copy is replaced entirely, so files from an earlier build don't
+// linger. Its .gitkeep, the only file there that's committed, is put back:
+// Go can't embed a directory that doesn't exist.
+import { cpSync, existsSync, rmSync, writeFileSync } from 'node:fs';
+
+const source = 'dist';
+const target = '../internal/frontend/dist';
+
+if (!existsSync(`${source}/index.html`)) {
+  console.error(`${source}/index.html not found: run npm run build first`);
+  process.exit(1);
+}
+
+rmSync(target, { recursive: true, force: true });
+cpSync(source, target, { recursive: true });
+writeFileSync(`${target}/.gitkeep`, '');
+
+console.log(`Copied ${source}/ to ${target}/`);