fix mobile responsiveness issues

- Fixed malformed .mobile-nav-btn CSS syntax
- Added global overflow-x: hidden to prevent horizontal scroll
- Made projects.js use consistent sidebar overlay approach
- Removed hardcoded min-width: 450px from all modals
- Added safe area insets for notched mobile devices
- Hamburger menu now appears on ALL views on mobile
- Sidebar slides in as overlay on mobile
- All touch targets are at least 44px
- Font sizes are at least 16px to prevent iOS zoom
- Modals are full-width on mobile

public/js/views/projectView.js

@@ -290,7 +290,7 @@ window.showNewFolderModal = async function(projectId, parentId) {
   const backdrop = document.createElement('div');
   backdrop.className = 'modal-backdrop';
   backdrop.innerHTML = `
-    <div class="modal" style="min-width: 450px;">
+    <div class="modal">
       <div class="modal-header">
         <span>📁</span>
         <h3>Create New Folder</h3>
@@ -366,7 +366,7 @@ window.showEditProjectModal = async function(projectId) {
   const backdrop = document.createElement('div');
   backdrop.className = 'modal-backdrop';
   backdrop.innerHTML = `
-    <div class="modal" style="min-width: 450px;">
+    <div class="modal">
       <div class="modal-header">
         <span>✏️</span>
         <h3>Edit Project</h3>
@@ -454,7 +454,7 @@ window.showMoveToFolderModal = async function(documentId) {
   const backdrop = document.createElement('div');
   backdrop.className = 'modal-backdrop';
   backdrop.innerHTML = `
-    <div class="modal" style="min-width: 450px;">
+    <div class="modal">
       <div class="modal-header">
         <span>📁</span>
         <h3>Move to Folder</h3>
@@ -507,7 +507,7 @@ window.showNewDocModal = async function(projectId, folderId = '') {
   backdrop.className = 'modal-backdrop';
   
   backdrop.innerHTML = `
-    <div class="modal" style="min-width: 450px;">
+    <div class="modal">
       <div class="modal-header">
         <span>📄</span>
         <h3>Create New Document</h3>