Boss Battle Mechanic: Add Boss Word at 1000 Points

[vivinarya]

Problem: The game is repetitive and needs climactic moments.

Task:

• Every 1000 points, stop spawning normal enemies and spawn a "Boss Word" (e.g., a very long string like "Supercalifragilistic").
• Give the boss word a health bar and slow movement.
• Return to spawning normal enemies after the boss is cleared.

Acceptance Criteria:

• Boss word appears at every 1000 points, normal enemies pause.
• Visible health bar for the boss.
• Boss moves slower than regular enemies.
• Code in script.js.