perf: lazy-load xlsx/recharts, split estimate tabs, memoize nav

- xlsx dynamically imported via cached singleton in excel.ts and
  skillMatrixParser.ts (removes ~100 kB from 4 routes)
- recharts extracted into lazy-loaded SkillDistributionChart and
  PeakTimesChart components (removes ~60 kB from 3 routes)
- EstimateWorkspaceClient: 7 tab components + 2 editors loaded via
  next/dynamic (reduces /estimates/[id] from 323 kB to 138 kB)
- ImportModal lazy-loaded in ResourcesClient (deferred until open)
- NavItem memoized with React.memo, top 5 routes get prefetch=true
- Raw <img> replaced with next/image in ProjectsClient, CoverArtSection
- tRPC QueryClient: refetchOnWindowFocus/Reconnect disabled globally

Heaviest routes reduced 39-66% First Load JS:
  /analytics/skills: 383→132 kB (-66%)
  /estimates/[id]:   323→138 kB (-57%)
  /resources/[id]:   458→210 kB (-54%)
  /estimates:        310→170 kB (-45%)
  /resources:        363→222 kB (-39%)

Co-Authored-By: claude-flow <ruv@ruv.net>

apps/web/src/lib/skillMatrixParser.ts

@@ -1,6 +1,14 @@
-import * as XLSX from "xlsx";
 import type { SkillEntry } from "@planarchy/shared";
 
+let _xlsx: typeof import("xlsx") | null = null;
+
+async function getXLSX() {
+  if (!_xlsx) {
+    _xlsx = await import("xlsx");
+  }
+  return _xlsx;
+}
+
 export interface ParsedEmployeeInfo {
   displayName?: string;
   areaOfExpertise?: string;
@@ -82,7 +90,8 @@ function parseSkillSheet(rows: Record<string, string>[], mainSkillSet: Set<strin
  * Parse a skill matrix workbook (xlsx ArrayBuffer) into structured data.
  * Returns ParsedSkillMatrix with employeeInfo and merged skills array.
  */
-export function parseSkillMatrixWorkbook(data: ArrayBuffer): ParsedSkillMatrix {
+export async function parseSkillMatrixWorkbook(data: ArrayBuffer): Promise<ParsedSkillMatrix> {
+  const XLSX = await getXLSX();
   const workbook = XLSX.read(new Uint8Array(data), { type: "array" });
 
   const employeeSheet = workbook.Sheets["Employee Information"];