refactor: centralize theme/config/utils + fix data and console bugs

Phase 1 of the cohesion refactor (behavior-preserving):

Single source of truth:
- New src/lib/theme.ts: category colors (moved from data.ts, re-exported
  for back-compat), derived hex strings, nebula palette, UI colors, CSS var map
- New src/lib/config.ts: breakpoint, zoom, parallax, node radii, particle
  counts, animation timings (previously scattered magic numbers)
- New src/lib/utils/tree.ts: getNodeById, getNodeRadius, getDistanceFromOrigin,
  getBeamIntensity (pure helpers lifted out of onMount)
- New src/lib/utils/stats.ts: branch ids/labels, proficiency order, and the
  stats-panel aggregation helpers (deduped from inline copies)
- SkillTree.svelte now imports all of the above; removed the duplicated
  getCategoryColorHex, stats helpers, branch id/label lists, and inline magic numbers
- Populated src/lib/index.ts barrel

Bug fixes:
- data.ts: tmdbAPI pypiUrl pointed at tvdbAPI -> corrected to tmdbAPI
- Removed/ gated stray console.log noise (skill-tree-loaded, SW logs)
- Removed dead vars (maxAlpha, glowMaxAlpha) and unused catch binding

Tooling: ESLint + Prettier now clean; added Vitest unit tests for the new
pure utils (14 tests). svelte-check: 0 errors. build: ok.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/lib/data.ts

@@ -300,7 +300,7 @@ export const treeNodes: TreeNode[] = [
 		icon: '/icons/python.svg',
 		techStack: ['Python', 'REST API', 'PyPI', 'GitHub Actions', 'Unit Testing'],
 		repoUrl: 'https://github.com/TehRiehlDeal/tmdbAPI',
-		pypiUrl: 'https://pypi.org/project/tvdbAPI/',
+		pypiUrl: 'https://pypi.org/project/tmdbAPI/',
 		status: 'maintained'
 	},
 	{
@@ -895,11 +895,6 @@ export const treeNodes: TreeNode[] = [
 	// },
 ];
 
-// Colors for each category (PoE-inspired)
-export const categoryColors: Record<TreeNode['category'], number> = {
-	origin: 0xffd700, // Gold
-	experience: 0x4ecdc4, // Teal
-	projects: 0xff6b6b, // Coral red
-	skills: 0xf9a825, // Amber orange
-	education: 0xdda0dd // Plum purple
-};
+// Category colours now live in `$lib/theme` (single source of truth).
+// Re-exported here for back-compat with existing `$lib/data` imports.
+export { categoryColors } from './theme';