chore(deps): upgrade major dependencies (ESLint 10, recharts 3, TS 6, Vite 8) (#130)

* chore(deps): upgrade ESLint 9 → 10 with plugin compatibility fixes

- eslint: ^9 → ^10.0.0 (backend + frontend)
- @eslint/js: ^9 → ^10.0.0 (backend + frontend)
- eslint-plugin-react-refresh: ^0.4.24 → ^0.5.2 (ESM, config factory API)
- Update frontend eslint.config.js: destructured import for react-refresh,
  call configs.vite() as factory function (0.5 API change)
- Downgrade new ESLint 10 rules (no-useless-assignment, preserve-caught-error)
  to warnings for existing code patterns
- eslint-plugin-react-hooks stays at 7.0.1 (stable) with --legacy-peer-deps
  until a stable release adds ESLint 10 peer support

* chore(deps): upgrade recharts 2.x to 3.8 with chart.tsx type fixes

recharts 3.x moved Tooltip/Legend props to context-based API.
Updated chart.tsx to use explicit prop interfaces with internal
recharts type imports (LegendPayload, TooltipPayload, TooltipFormatter).

* chore(deps): upgrade TypeScript 5.9 to 6.0

- Remove deprecated baseUrl from frontend tsconfig (paths works standalone in TS 6)
- Add react-is dependency required by recharts 3.x at build time
- Backend and frontend both compile and lint cleanly

* chore(deps): upgrade Vite 7.3 to 8.0 and @vitejs/plugin-react to 6.0

Vite 8 replaces Rollup+esbuild with Rolldown, significantly improving
build speed (~2s vs ~18s). No config changes required.

* fix(ci): add .npmrc with legacy-peer-deps for CI and Docker builds

typescript-eslint@8.x requires typescript <6.0.0 and
eslint-plugin-react-hooks@7.0.1 requires eslint <=9. Until upstream
packages release compatible versions, legacy-peer-deps is needed.

* docs: add logo assets and re-ignore CLAUDE.md

* fix(ci): copy .npmrc into prod-deps Docker stage

The prod-deps stage also runs npm ci with backend/package.json but was
missing the .npmrc needed to bypass peer dep conflicts.

Dockerfile

@@ -9,7 +9,7 @@ FROM --platform=$BUILDPLATFORM node:20-alpine AS frontend-builder
 
 WORKDIR /app/frontend
 
-COPY frontend/package*.json ./
+COPY frontend/package*.json frontend/.npmrc ./
 RUN npm config set fetch-retry-maxtimeout 120000 && \
     npm config set fetch-retries 5 && \
     npm install
@@ -25,7 +25,7 @@ WORKDIR /app/backend
 
 RUN apk add --no-cache python3 make g++
 
-COPY backend/package*.json ./
+COPY backend/package*.json backend/.npmrc ./
 RUN npm config set fetch-retry-maxtimeout 120000 && \
     npm config set fetch-retries 5 && \
     npm install
@@ -69,7 +69,7 @@ RUN if [ "$TARGETARCH" = "$BUILDARCH" ]; then \
       xx-apk add --no-cache g++ musl-dev linux-headers; \
     fi
 
-COPY backend/package*.json ./
+COPY backend/package*.json backend/.npmrc ./
 
 # Native: plain npm ci — g++ compiles native modules for the host arch.
 # Cross:  npm_config_arch tells prebuild-install/node-pre-gyp which pre-built