feat!: Split site into public and private sections

Moved the Copper Chronicle and resume into a private git submodule
(src/private), visible only to authenticated users. Added a lock symbol
to the mdbook sidebar for restricted sections. Reorganized nginx/nix
configuration files into a dedicated folder. Removed one-line descriptions
from the menu. Reduced custom CSS to better align the main website's theme
with mdbook's native styling. Personalized the index and blog introduction
pages.

src/recipes/desserts/roasted-peaches-with-honey-mint-and-ice-cream.md

@@ -0,0 +1,15 @@
+*Source: Abby*
+
+## Ingredients
+- Fresh peaches, halved and pitted
+- Honey
+- Fresh mint leaves
+- Vanilla ice cream
+- Butter
+- Optional: cinnamon
+
+## Instructions
+1. Place peach halves cut-side up in baking dish.
+2. Drizzle with honey, dot with butter.
+3. Roast at 375°F for 20-25 minutes until tender.
+4. Serve warm with ice cream and fresh mint.