chore: remove cms and fix some styles (#29)

* chore: remove all references to PayloadCMS

* fix: nextjs landing utils

* feat: refactor community, features, hero, learning resources, and testimonials components to use external JSON data

* fix:remove hero logo box

* fix: remove unused image in public

* fix: change logo.png to logo.webp

* fix: update button styles for improved visibility

* chore: restructure component organization

* fix: update import path for global styles in layout component

* fix: adjust alignment of hero stats section for better layout

* fix: update testimonials placeholder sample data

* fix: update header component to use router for navigation and add signin page

apps/landing/src/data/testimonials.json

@@ -0,0 +1,20 @@
+[
+  {
+    "quote": "Sebagai seseorang yang awalnya buta sama sekali tentang programming, kini saya bisa membuat website sendiri dengan percaya diri. IMPHNEN benar-benar jadi pintu gerbang saya ke dunia web development!",
+    "name": "Ega",
+    "role": "Web Developer",
+    "avatar": "https://avatars.githubusercontent.com/u/97678571?v=4"
+  },
+  {
+    "quote": "IMPHNEN bukan cuma komunitas, tapi juga jadi tempat saya berkembang sebagai backend engineer. Diskusi teknisnya berbobot, dan respon dari komunitas selalu cepat dan tepat sasaran.",
+    "name": "Maulana",
+    "role": "Backend Engineer",
+    "avatar": "https://avatars.githubusercontent.com/u/53475078?v=4"
+  },
+  {
+    "quote": "Sebagai fullstack engineer pemula, saya merasa sangat terbantu dengan komunitas Discord IMPHNEN. Materinya praktikal, pembahasannya jelas, dan member-nya selalu siap membantu.",
+    "name": "Rasyid",
+    "role": "Fullstack Engineer",
+    "avatar": "https://avatars.githubusercontent.com/u/49753444?v=4"
+  }
+]