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/red-wine-pears.md

@@ -0,0 +1,16 @@
+*Source: Abby*
+
+## Ingredients
+- Pears, peeled (stems intact)
+- Red wine
+- Sugar or honey
+- Cinnamon stick
+- Star anise
+- Vanilla bean or extract
+- Orange peel
+
+## Instructions
+1. Combine wine, sweetener, and spices in pot.
+2. Add pears, simmer 20-30 minutes, turning occasionally.
+3. Remove pears, reduce liquid to syrup.
+4. Serve pears with syrup drizzled over.