fix(ui): clean up window event listeners and ResizeObserver in destroy()

[NewCoder3294]

Summary

Multiple components add window-level event listeners using anonymous callbacks, making them impossible to remove when destroy() is called. This causes memory leaks as listeners accumulate across component mount/unmount cycles (e.g., when switching views or panels).

The pattern fixed in each component:

• Anonymous callback passed to addEventListener → stored as a named class property
• destroy() now calls removeEventListener with the same function reference

Components fixed

• CountryTimeline.ts — theme-changed listener was never removed in destroy(). Stored handler as this.handleThemeChange, added removeEventListener call in destroy().
• DeckGLMap.ts — theme-changed listener was never removed in destroy(). Same fix pattern.
• Map.ts — Two leaks fixed:
  1. theme-changed listener was never removed in destroy(). Same fix pattern.
  2. ResizeObserver was created as a local variable inside setupResizeObserver(), so it could never be disconnected. Promoted to this.resizeObserver class property and added disconnect() call in destroy().

Note: BreakingNewsBanner.ts was also audited but already correctly stores all handler references and removes them in its destroy() method — no changes needed.

Test plan

• Verify TypeScript compiles cleanly (tsc --noEmit — confirmed passing in CI pre-push hook)
• Mount and destroy CountryTimeline, DeckGLMap, and Map components repeatedly; confirm no accumulating theme-changed listeners via DevTools Event Listeners panel
• Toggle theme after component destruction; confirm no errors from stale listeners
• Resize browser window after Map component destruction; confirm no errors from stale ResizeObserver

🤖 Generated with Claude Code

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