Full codebase cleanup and optimization pass

- Fix all hardcoded light colors breaking dark mode (FileAttachment, TaskDetail, RequestDetail)
- Parallelize sequential DB fetches in TaskDetail, CompanyDetail, MyProjects
- Add error handling: NewRequest project/file upload, MyCompany update, CompanyDetail prices, AuthContext profile fetch
- Fix currentUser.company_id → currentUser.company?.id in NewRequest
- Remove stale company.email references from InvoiceDetail, ProjectDetail, TaskDetail
- Clean up dead email field from Companies form reset

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/components/FileAttachment.jsx

@@ -46,7 +46,7 @@ export default function FileAttachment({ files, onChange }) {
       <div style={{
         border: `2px dashed ${files.length > 0 ? 'var(--accent)' : 'var(--border)'}`,
         borderRadius: 8, padding: '18px 16px', textAlign: 'center',
-        background: files.length > 0 ? '#fffbeb' : '#fafafa', transition: 'all 0.15s',
+        background: 'var(--bg)', transition: 'all 0.15s',
       }}>
         <input type="file" multiple onChange={handleChange} style={{ display: 'none' }} id="req-file-upload" />
         <label htmlFor="req-file-upload" style={{ cursor: 'pointer' }}>
@@ -67,7 +67,7 @@ export default function FileAttachment({ files, onChange }) {
           {files.map((file, i) => (
             <div key={i} style={{
               display: 'flex', alignItems: 'center', justifyContent: 'space-between',
-              padding: '7px 12px', background: 'white', borderRadius: 8, border: '1px solid var(--border)',
+              padding: '7px 12px', background: 'var(--card-bg)', borderRadius: 8, border: '1px solid var(--border)',
             }}>
               <div style={{ display: 'flex', alignItems: 'center', gap: 8 }}>
                 <span>📄</span>