feat: architecture refactor — core layer, spreadsheet engine, envelope bidding, tests

- Add src/core/ (config, errors, events, http, observability, storage, query)
- Add src/Spreadsheet/ engine with native POI backend and Excel bridge
- Add Envelope C spreadsheet flow and tender bidding envelope modules
- Consolidate components into src/components/, remove legacy Component/ and Hooks/
- Add registration state/validation, auth session guard, profile edit modules
- Add unit tests across axios, redux, bidding, registration, encryption, core
- Add CI workflow, docs (architecture, audit, DSC API spec), keystore example
- Remove tracked keystore binary; ignore scripts.zip

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

src/Spreadsheet/hooks/useGridTheme.ts

@@ -0,0 +1,63 @@
+/**
+ * Derives a spreadsheet-specific palette from the app theme so the grid matches
+ * the product and supports light + dark mode out of the box.
+ */
+import { useMemo } from 'react';
+import { useTheme } from '../../Hooks/useTheme';
+
+export interface GridTheme {
+  isDark: boolean;
+  background: string;
+  gridLine: string;
+  headerBg: string;
+  headerText: string;
+  headerActiveBg: string;
+  cellText: string;
+  mutedText: string;
+  selectionFill: string;
+  selectionBorder: string;
+  laneHighlight: string;
+  readOnlyBg: string;
+  errorBorder: string;
+  errorFill: string;
+  editorBg: string;
+  editorBorder: string;
+  searchHighlight: string;
+  lockIcon: string;
+  primary: string;
+  surface: string;
+}
+
+export const useGridTheme = (): GridTheme => {
+  const { colors, isDarkMode } = useTheme();
+
+  return useMemo<GridTheme>(
+    () => ({
+      isDark: isDarkMode,
+      background: isDarkMode ? '#1b1c1d' : '#ffffff',
+      gridLine: isDarkMode ? 'rgba(255,255,255,0.12)' : 'rgba(15,23,42,0.12)',
+      headerBg: isDarkMode ? '#2b2c2e' : '#f1f5f9',
+      headerText: isDarkMode ? '#cbd5e1' : '#475569',
+      headerActiveBg: colors.primary,
+      cellText: colors.text,
+      mutedText: colors.textSecondary,
+      selectionFill: isDarkMode ? 'rgba(227,149,70,0.20)' : 'rgba(227,149,70,0.16)',
+      selectionBorder: colors.primary,
+      laneHighlight: isDarkMode ? 'rgba(227,149,70,0.10)' : 'rgba(227,149,70,0.08)',
+      readOnlyBg: isDarkMode ? 'rgba(255,255,255,0.05)' : 'rgba(15,23,42,0.045)',
+      errorBorder: colors.error,
+      errorFill: isDarkMode ? 'rgba(248,113,113,0.16)' : 'rgba(239,68,68,0.10)',
+      editorBg: colors.surface,
+      editorBorder: colors.primary,
+      searchHighlight: isDarkMode ? 'rgba(253,186,116,0.30)' : 'rgba(253,186,116,0.45)',
+      lockIcon: '#000000',
+      primary: colors.primary,
+      surface: colors.surface,
+    }),
+    [colors, isDarkMode],
+  );
+};
+
+export default useGridTheme;
+
+