feat: e2eビルド時にanalyticsイベントの送信を無効化

[Copilot]

e2eビルド（--mode e2e）時にGA（Google Analytics）へイベントが送信されてしまう問題を修正。

変更点

• analytics.ts の DISABLE_ANALYTICS フラグに isE2E 条件を追加

// Before
const DISABLE_ANALYTICS = IS_CI

// After
const DISABLE_ANALYTICS = IS_CI || isE2E

isE2E は import.meta.env.MODE === "e2e" で評価されるコンパイル時定数。yarn build:e2e（Vite --mode e2e）でビルドされた場合のみ true となる。

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 25.66%. Comparing base (0cdb2f6) to head (08f82e1).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #356   +/-   ##
=======================================
  Coverage   25.66%   25.66%           
=======================================
  Files         309      309           
  Lines       31240    31240           
  Branches     1546     1547    +1     
=======================================
  Hits         8017     8017           
  Misses      23223    23223           

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