feat: integrate Cal.com popup booking via @calcom/embed-react

- CalButton component: loads Cal.com embed script, triggers popup on click
- Configured for scheduling.letsbe.solutions (self-hosted)
- Wired into configurator completion step (Book a Call)
- Wired into footer Book a Call button
- Brand colors: #006494 light, #5BA4D9 dark

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

package-lock.json

@@ -7,8 +7,8 @@
     "": {
       "name": "letsbe-agency",
       "version": "1.0.0",
-      "license": "ISC",
       "dependencies": {
+        "@calcom/embed-react": "^1.5.3",
         "@payloadcms/db-postgres": "^3.80.0",
         "@payloadcms/next": "^3.80.0",
         "@payloadcms/richtext-lexical": "^3.80.0",
@@ -215,6 +215,35 @@
         "url": "https://github.com/sponsors/Borewit"
       }
     },
+    "node_modules/@calcom/embed-core": {
+      "version": "1.5.3",
+      "resolved": "https://registry.npmjs.org/@calcom/embed-core/-/embed-core-1.5.3.tgz",
+      "integrity": "sha512-GeId9gaByJ5EWiPmuvelZOvFWPOTWkcWZr5vGTCbIUTX125oE5yn0n8lDF1MJk5Xj1WO+/dk9jKIE08Ad9ytiQ==",
+      "license": "SEE LICENSE IN LICENSE"
+    },
+    "node_modules/@calcom/embed-react": {
+      "version": "1.5.3",
+      "resolved": "https://registry.npmjs.org/@calcom/embed-react/-/embed-react-1.5.3.tgz",
+      "integrity": "sha512-JCgge04pc8fhdvUmPNVLhW8/lCWK+AAziKecKWWPfv1nn2s+qKP2BwsEAnxhxK9yPOBgE1EIEgmYkrrNB1iajA==",
+      "license": "SEE LICENSE IN LICENSE",
+      "dependencies": {
+        "@calcom/embed-core": "1.5.3",
+        "@calcom/embed-snippet": "1.3.3"
+      },
+      "peerDependencies": {
+        "react": "^18.2.0 || ^19.0.0",
+        "react-dom": "^18.2.0 || ^19.0.0"
+      }
+    },
+    "node_modules/@calcom/embed-snippet": {
+      "version": "1.3.3",
+      "resolved": "https://registry.npmjs.org/@calcom/embed-snippet/-/embed-snippet-1.3.3.tgz",
+      "integrity": "sha512-pqqKaeLB8R6BvyegcpI9gAyY6Xyx1bKYfWvIGOvIbTpguWyM1BBBVcT9DCeGe8Zw7Ujp5K56ci7isRUrT2Uadg==",
+      "license": "SEE LICENSE IN LICENSE",
+      "dependencies": {
+        "@calcom/embed-core": "1.5.3"
+      }
+    },
     "node_modules/@date-fns/tz": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/@date-fns/tz/-/tz-1.2.0.tgz",