fix(web): add safe-area-inset-top padding to prevent statusbar overlap on iOS PWA

This fixes an issue where viewport-fit=cover and black-translucent statusbar
configuration allowed content to extend under the iOS statusbar. Added env(safe-area-inset-top)
CSS handling to all main layout components:
- SessionHeader with pt-[env(safe-area-inset-top)]
- SessionsPage, MachinesPage, SpawnPage with safe-area padding
- FilesPage and FilePage headers with safe-area padding

web/src/routes/sessions/file.tsx

@@ -175,7 +175,7 @@ export default function FilePage() {
 
     return (
         <div className="flex h-full flex-col">
-            <div className="bg-[var(--app-bg)] border-b border-[var(--app-border)]">
+            <div className="bg-[var(--app-bg)] border-b border-[var(--app-border)] pt-[env(safe-area-inset-top)]">
                 <div className="mx-auto w-full max-w-[720px] flex items-center gap-2 p-3">
                     <button
                         type="button"

web/src/routes/sessions/files.tsx

@@ -249,7 +249,7 @@ export default function FilesPage() {
 
     return (
         <div className="flex h-full flex-col">
-            <div className="bg-[var(--app-bg)] border-b border-[var(--app-border)]">
+            <div className="bg-[var(--app-bg)] border-b border-[var(--app-border)] pt-[env(safe-area-inset-top)]">
                 <div className="mx-auto w-full max-w-[720px] flex items-center gap-2 p-3">
                     <button
                         type="button"