refactor: align views with upstream @indiekit/frontend patterns

- Extract ~560 lines of inline CSS to external assets/styles.css
- Create intermediate layout (layouts/blogroll.njk) for CSS loading
- Use section(), badge(), button(), prose() macros instead of raw HTML
- Remove custom page headers (document.njk heading() handles via title/parent)
- Add parent breadcrumb navigation to all sub-pages
- Add consumeFlashMessage() to dashboard and sources controllers
- Rename CSS class prefix from br-* to blogroll-* for clarity
- Use upstream CSS custom properties without fallback values
- Fix Microsub orphan detection (soft-delete unsubscribed blogs)
- Fix upsert to conditionally set microsub fields (avoid path conflicts)
- Skip soft-deleted blogs during clear-and-resync

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@rmdes/indiekit-endpoint-blogroll",
-  "version": "1.0.12",
+  "version": "1.0.15",
   "description": "Blogroll endpoint for Indiekit. Aggregates blog feeds from OPML, JSON feeds, or manual entry.",
   "keywords": [
     "indiekit",