Add JSDoc and inline documentation to App.jsx

[Copilot]

Adds comprehensive documentation to the superhero comparison application's main component.

Changes

• File-level JSDoc: Module description covering application purpose and two-view architecture
• Function JSDoc: Complete parameter and return type documentation for all 8 functions (App, handleHeroSelection, isHeroSelected, handleCompare, handleBackToTable, calculateWinner, renderComparison, renderTable)
• Inline comments: State variable purposes, FIFO selection behavior, winner calculation logic, and JSX section markers

Example

/**
 * Calculates the winner between two heroes based on their power stats.
 * 
 * Compares six stats (intelligence, strength, speed, durability, power, combat) and
 * awards a point to the hero with the higher value in each category. The hero with
 * more points wins.
 * 
 * @param {Object} hero1 - The first hero to compare
 * @param {Object} hero1.powerstats - The power statistics object
 * @param {number} hero1.powerstats.intelligence - Intelligence stat
 * // ... [additional stats]
 * @returns {{winner: Object|null, score: string}} Object containing the winner (or null for tie) and score string
 */
const calculateWinner = (hero1, hero2) => {
  // Compare each stat and award points to the hero with higher value
  stats.forEach(stat => {
    if (hero1.powerstats[stat] > hero2.powerstats[stat]) {
      hero1Score++;
    } else if (hero2.powerstats[stat] > hero1.powerstats[stat]) {
      hero2Score++;
    }
    // No points awarded if stats are equal
  });
  // ...
};

Original prompt

---

This section details on the original issue you should resolve

<issue_title>Add documentation to frontend/src/App.jsx</issue_title>
<issue_description>Add documentation to frontend/src/App.jsx:

• Overall file doc
• Function docs
• Inline docs</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Add documentation to frontend/src/App.jsx #4

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