fix(ci): exclude project-local pnpm store from lint/format scans

CI runners configure pnpm with --store-dir=.pnpm-store (project-local
CAS) for cross-run caching. Prettier and ESLint were scanning into it
and finding 333 unformatted JSON files.

Added to .prettierignore and eslint.config.js globalIgnores:
- .pnpm-store / .pnpm — pnpm content-addressable store variants
- coverage — future test runs (Vitest in Phase 3)
- .cache — generic build cache directory

Local Windows trees aren't affected (pnpm uses the global store at
~/.local/share/pnpm/store) but the rules cover both paths.

.prettierignore

@@ -1,8 +1,13 @@
 node_modules
+.pnpm-store
+.pnpm
 dist
 dist-ssr
+coverage
+.cache
 pnpm-lock.yaml
 *.log
 .git
 public
 src/routeTree.gen.ts
+