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/excel.ts

@@ -1,37 +1,32 @@
-import * as XLSX from "xlsx";
+let _xlsx: typeof import("xlsx") | null = null;
+
+async function getXLSX() {
+  if (!_xlsx) {
+    _xlsx = await import("xlsx");
+  }
+  return _xlsx;
+}
 
 /**
  * Parse an Excel (.xlsx, .xls) or CSV file to an array of row objects.
  * Keys come from the first row (headers).
  */
-export function parseSpreadsheet(file: File): Promise<Record<string, string>[]> {
-  return new Promise((resolve, reject) => {
-    const reader = new FileReader();
-    reader.onload = (e) => {
-      try {
-        const data = new Uint8Array(e.target!.result as ArrayBuffer);
-        const workbook = XLSX.read(data, { type: "array" });
-        const sheetName = workbook.SheetNames[0];
-        if (!sheetName) {
-          resolve([]);
-          return;
-        }
-        const sheet = workbook.Sheets[sheetName];
-        if (!sheet) {
-          resolve([]);
-          return;
-        }
-        const rows = XLSX.utils.sheet_to_json<Record<string, string>>(sheet, {
-          raw: false,
-          defval: "",
-        });
-        resolve(rows);
-      } catch (err) {
-        reject(err);
-      }
-    };
-    reader.onerror = () => reject(reader.error);
-    reader.readAsArrayBuffer(file);
+export async function parseSpreadsheet(file: File): Promise<Record<string, string>[]> {
+  const XLSX = await getXLSX();
+  const buffer = await file.arrayBuffer();
+  const data = new Uint8Array(buffer);
+  const workbook = XLSX.read(data, { type: "array" });
+  const sheetName = workbook.SheetNames[0];
+  if (!sheetName) {
+    return [];
+  }
+  const sheet = workbook.Sheets[sheetName];
+  if (!sheet) {
+    return [];
+  }
+  return XLSX.utils.sheet_to_json<Record<string, string>>(sheet, {
+    raw: false,
+    defval: "",
   });
 }