refactor: remove @material-ui/icons@4 in favor of @mui/icons-material@5 (#179)

* refactor: remove @material-ui/icons@4 in favor of @mui/icons-material@5

All icon imports were already using @mui/icons-material, so this removes
the unused @material-ui/icons@4 dependency. Updated .npmrc comment to
reflect the remaining peer conflict (due to @mui/styles@5 requiring
@types/react@^17.0.0).

Closes #175

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: clarify legacy-peer-deps comment to include react peer conflict

@mui/styles@5 requires both react@^17.0.0 and @types/react@^17.0.0,
not just the types package. Update comment to avoid the impression that
fixing the type definitions alone would allow removing the flag.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

* fix: apply Copilot suggestion for legacy-peer-deps comment

Spell out the exact package version and both peer deps (react and
@types/react) for clarity, per Copilot review on PR #179.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

---------

Co-authored-by: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: ryaukwan

.npmrc

@@ -1,3 +1,2 @@
-# Required until @material-ui/icons@4 is migrated to @mui/icons-material@5 (see issue #175).
-# @material-ui/icons@4 has an unresolved peer dependency conflict with React 18.
+# Required because @mui/styles@5.10.10 declares peer dependencies on react@^17.0.0 and @types/react@^17.0.0, while the project uses React 18 and @types/react@^18.0.0.
 legacy-peer-deps=true

package-lock.json

@@ -12,7 +12,6 @@
   "dependencies": {
     "@emotion/react": "^11.10.5",
     "@emotion/styled": "^11.10.5",
-    "@material-ui/icons": "^4.11.3",
     "@mui/icons-material": "^5.10.9",
     "@mui/material": "^5.10.13",
     "@mui/styles": "^5.10.10",