fix: Remove Number() conversions that corrupt uint64 IDs

JavaScript's Number type cannot accurately represent uint64 values exceeding
Number.MAX_SAFE_INTEGER (2^53-1). Converting these IDs to numbers causes
precision loss and API errors.

Root cause found:
- match/[id]/+layout.ts: `Number(params.id)` corrupted match IDs
- player/[id]/+page.ts: `Number(params.id)` corrupted player IDs

Example of the bug:
- URL param: "3638078243082338615" (correct)
- After Number(): 3638078243082339000 (rounded!)
- API response: "Match 3638078243082339000 not found"

Changes:
- Remove Number() conversions in route loaders
- Keep params.id as string throughout the application
- Update API functions to only accept string (not string | number)
- Update MatchesQueryParams.player_id type to string
- Add comprehensive transformers for legacy API responses
- Transform player stats: duo→mk_2, triple→mk_3, steamid64→id
- Build full Steam avatar URLs
- Make share_code optional (not always present)

This ensures uint64 IDs maintain full precision from URL → API → response.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

src/routes/player/[id]/+page.ts

@@ -3,9 +3,9 @@ import { api } from '$lib/api';
 import type { PageLoad } from './$types';
 
 export const load: PageLoad = async ({ params }) => {
-	const playerId = Number(params.id);
+	const playerId = params.id; // Keep as string to preserve uint64 precision
 
-	if (isNaN(playerId) || playerId <= 0) {
+	if (!playerId || playerId.trim() === '') {
 		throw error(400, 'Invalid player ID');
 	}