Migrate from better-sqlite3 to Cloudflare D1

[gcarvelli]

Summary

Replace better-sqlite3 and filesystem imports in src/lib/db/index.ts with Cloudflare D1 API. All database functions are now async and use D1 bindings from process.env, resolving the "Operation not permitted" error in Cloudflare Workers.

Changes

• Rewrote src/lib/db/index.ts to use D1 async API instead of better-sqlite3
• Removed all fs/path imports and filesystem access (schema loading, WAL pragmas, migrations)
• Deleted redundant src/lib/db/d1.ts adapter
• Updated 11 consumers (3 server components, 8 API routes) to use await for all DB calls
• Build succeeds with no errors; app bundle contains zero better-sqlite3 or fs imports

Test Plan

• ✓ npm run build — Production build succeeds
• Run npx wrangler dev to test with local D1 simulator
• Deploy to Cloudflare Workers to verify "Operation not permitted" is resolved