Unify Further Reading into one styled box (CF-3115)

- Template renders one Further Reading aside (essential-reading style)
  with author-curated list + auto-appended layers-of-protection pillar
- Removed separate Essential reading aside
- Migrated 10 articles' ## Further Reading sections into frontmatter
  further_reading: translationKey arrays
- Added further_reading i18n key in en/de/fr

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

content/en/parental-controls-2026-practical-guide.md

@@ -7,6 +7,9 @@ categories: ["safety"]
 author: "Agiliton"
 slug: "parental-controls-2026-practical-guide"
 translationKey: "parental-controls-2026"
+further_reading:
+  - "is-tiktok-safe"
+  - "roblox-fortnite-discord-guide"
 ---
 
 There is no single "parental control" that works. Every family eventually learns this the same way — they set up Screen Time on an iPad, watch their ten-year-old bypass it in an afternoon, and start searching for a better answer. The better answer is not a different product. It is a layered setup that plays each tool to its strengths.
@@ -72,9 +75,3 @@ We trim the raw upstream lists to roughly 15-30,000 domains optimised for German
 - **Router filtering only.** Protects the house, fails the moment they're on mobile data or friends' Wi-Fi.
 - **VPN only.** Doesn't limit time spent in the apps that *are* allowed. You still need device-level limits.
 - **No conversation.** Produces sneaky teenagers, not safe ones.
-
-## Further Reading
-
-- [Is TikTok Safe for My Child?](/en/is-tiktok-safe-for-kids/)
-- [Safe Search and Content Filtering: What Actually Works in 2026](/en/safe-search-content-filtering-2026/)
-- [Roblox, Fortnite, Discord: Age Ratings and Real Risks](/en/roblox-fortnite-discord-age-ratings-risks/)