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/components/projects/CoverArtSection.tsx

@@ -1,6 +1,7 @@
 "use client";
 
 import { useState, useRef } from "react";
+import NextImage from "next/image";
 import { trpc } from "~/lib/trpc/client.js";
 
 interface CoverArtSectionProps {
@@ -149,14 +150,18 @@ export function CoverArtSection({ projectId, coverImageUrl, coverFocusY = 50, pr
       {/* Cover image or placeholder */}
       {imageUrl ? (
         <div className="relative">
-          <img
+          <NextImage
             src={imageUrl}
             alt={`Cover art for ${projectName}`}
+            width={1024}
+            height={1024}
             className="w-full object-cover"
             style={{
               height: "clamp(16rem, 22vw, 22rem)",
               objectPosition: `center ${focusY}%`,
             }}
+            unoptimized={imageUrl.startsWith("data:")}
+            priority
           />
           {/* Gradient overlay at bottom for readability */}
           <div className="absolute inset-x-0 bottom-0 h-16 bg-gradient-to-t from-black/40 to-transparent" />