fix: popups no longer close on backdrop click, only via explicit close/cancel

Clicking the dimmed area outside a modal (+Task, +Invoice, expense,
review, etc.) accidentally dismissed it and lost in-progress input.
Every popup already has an explicit Cancel/Close/✕ button, so the
backdrop click handler is removed; also drops the now-dead
onClose/blockClose prop plumbing that only existed to support it.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

src/pages/BrandBook.jsx

@@ -2353,7 +2353,6 @@ function DimensionEditorModal({ sourceImage, onApply, onCancel }) {
   return (
     <div
       style={{ ...popupOverlayStyle, zIndex: 9999, padding: 20 }}
-      onClick={(e) => { if (e.target === e.currentTarget) onCancel(); }}
     >
       <div style={{ ...popupSurfaceStyle, borderRadius: 8, display: 'flex', flexDirection: 'column', maxWidth: '98vw', maxHeight: '96vh', overflow: 'hidden', padding: 0 }}>
         <div style={{ padding: '12px 18px', borderBottom: '1px solid var(--border)', display: 'flex', alignItems: 'center', justifyContent: 'space-between', flexShrink: 0 }}>
@@ -3436,7 +3435,6 @@ function PhotoEditorModal({
   return (
     <div
       style={{ ...popupOverlayStyle, zIndex: 9999, padding: 20 }}
-      onClick={(e) => { if (e.target === e.currentTarget) onCancel(); }}
     >
       <div style={{ ...popupSurfaceStyle, borderRadius: 8, display: 'flex', flexDirection: 'column', maxWidth: '98vw', maxHeight: '96vh', overflow: 'hidden', padding: 0 }}>
         {/* Header */}