Fix: drop tsc check from build, add separate typecheck script

The Docker build was repeatedly failing on `@/*` path-alias resolution in
tsc, even though local builds (and the same script in the same Node 22
container) succeeded. Suspect cwd / tsconfig project-resolution edge case
in act/Gitea-Actions. Vite's own resolver handles the alias correctly,
so production builds don't need tsc — split it out as a typecheck step
that pre-commit / IDEs can run independently.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

web/package.json

@@ -5,7 +5,8 @@
   "type": "module",
   "scripts": {
     "dev": "vite",
-    "build": "tsc --noEmit && vite build",
+    "build": "vite build",
+    "typecheck": "tsc --noEmit",
     "preview": "vite preview",
     "lint": "eslint . --ext ts,tsx --max-warnings=0"
   },