fix: comprehensive TypeScript/build fixes and modernization

- Update tsconfig to ES2024 target and bundler moduleResolution
- Add dynamic imports for chart.js and recharts (bundle optimization)
- Consolidate 17 useState into useReducer in sessions page
- Fix 18 .js extension imports across lib files
- Add type declarations for @rapideditor/country-coder
- Fix platform user types (PlatformUserRole enum)
- Fix Calendar component prop types
- Centralize next-auth type augmentation
- Add force-dynamic to all API routes (prevent build-time prerender)
- Fix Prisma JSON null handling with Prisma.DbNull
- Fix various type mismatches (SessionMessage, ImportRecord, etc.)
- Export ButtonProps from button component
- Update next-themes import path
- Replace JSX.Element with React.ReactElement
- Remove obsolete debug scripts and pnpm lockfile
- Downgrade eslint to v8 for next compatibility

.github/skills/vercel-react-best-practices/rules/bundle-dynamic-imports.md

@@ -0,0 +1,35 @@
+---
+title: Dynamic Imports for Heavy Components
+impact: CRITICAL
+impactDescription: directly affects TTI and LCP
+tags: bundle, dynamic-import, code-splitting, next-dynamic
+---
+
+## Dynamic Imports for Heavy Components
+
+Use `next/dynamic` to lazy-load large components not needed on initial render.
+
+**Incorrect (Monaco bundles with main chunk ~300KB):**
+
+```tsx
+import { MonacoEditor } from './monaco-editor'
+
+function CodePanel({ code }: { code: string }) {
+  return <MonacoEditor value={code} />
+}
+```
+
+**Correct (Monaco loads on demand):**
+
+```tsx
+import dynamic from 'next/dynamic'
+
+const MonacoEditor = dynamic(
+  () => import('./monaco-editor').then(m => m.MonacoEditor),
+  { ssr: false }
+)
+
+function CodePanel({ code }: { code: string }) {
+  return <MonacoEditor value={code} />
+}
+```