feat: Polar license key integration and dashboard UI improvements

- Add license activation flow: server validates/activates keys via Polar SDK
- Auto-activate from Polar checkout redirect (checkout_id in URL)
- Gate dashboard behind license activation (redirect to /activate if no plan)
- Preserve redirect URL through login flow for post-purchase activation
- Show plan status badge in sidebar and overview page
- Add account section to settings (email, plan, license key)
- Add svelte-sonner toasts with custom black theme and iconify icons
- Improve validation messages across all forms
- Update API key prefix to droidclaw_
- Add cursor pointer globally for clickable elements
- Support Polar sandbox mode via POLAR_SANDBOX env flag

server/package.json

@@ -9,9 +9,10 @@
   },
   "dependencies": {
     "@droidclaw/shared": "workspace:*",
-    "hono": "^4.7.0",
+    "@polar-sh/sdk": "^0.43.1",
     "better-auth": "^1.3.27",
     "drizzle-orm": "^0.44.5",
+    "hono": "^4.7.0",
     "postgres": "^3.4.7"
   },
   "devDependencies": {