Remove dead BASE_URL and EXCLUDE_PATHS

Three files declare const BASE_URL = '' and use it in string concatenations — all no-ops. A separate EXCLUDE_PATHS list points at routes that don't exist in this project (carryover from the parent template).

Current State

• src/lib/url-utils.js:1
• src/lib/page-renderer.svelte.js:8
• src/routes/feed.xml/+server.js:23
• page-renderer.svelte.js:10-24 — EXCLUDE_PATHS with /blog/, /learning-center/..., /reviews/

Tasks

• Delete the three BASE_URL declarations and their usages
• Delete EXCLUDE_PATHS or replace with real exclusions