feat: upgrade to SvelteKit 3 and adapter-bun

Run the sveltekit-3 migration and finish its manual tasks:

- Move kit config into the sveltekit() Vite plugin; drop svelte.config.js
- Replace $lib with #lib subpath imports
- Declare env vars in src/env.ts and import them from $app/env/{private,public}
- Consolidate param matchers into src/params.ts
- Use error(status, message), Response.json, refreshAll and goto reset/shallow
- Fall back to a full page load when goto rejects a login return path

Switch from adapter-node to adapter-bun: the build script runs Vite under
Bun (the adapter requires it) and the image starts with `bun ./build`.
Runtime env names (PORT, BODY_SIZE_LIMIT, ADDRESS_HEADER, ...) are unchanged.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/routes/projects/animaldex/api/map/+server.ts

@@ -1,8 +1,8 @@
-import { json, error } from '@sveltejs/kit';
+import { error } from '@sveltejs/kit';
 import type { RequestHandler } from './$types';
-import { db } from '$lib/server/db';
-import { animals, sightings } from '$lib/server/db/schema';
-import { mapQuerySchema } from '$lib/validation/sighting';
+import { db } from '#lib/server/db/index.js';
+import { animals, sightings } from '#lib/server/db/schema/index.js';
+import { mapQuerySchema } from '#lib/validation/sighting.js';
 import { and, eq, gte, ilike, isNotNull, isNull, lte, sql } from 'drizzle-orm';
 
 export const GET: RequestHandler = async ({ url }) => {
@@ -10,7 +10,7 @@ export const GET: RequestHandler = async ({ url }) => {
 	const parsed = mapQuerySchema.safeParse(params);
 
 	if (!parsed.success) {
-		throw error(400, { message: 'Invalid query parameters' });
+		throw error(400, 'Invalid query parameters');
 	}
 
 	const q = parsed.data;
@@ -118,5 +118,5 @@ export const GET: RequestHandler = async ({ url }) => {
 		};
 	});
 
-	return json({ type: 'FeatureCollection', features });
+	return Response.json({ type: 'FeatureCollection', features });
 };