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/camping/cobblestacks-v2.md

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+*Source: Matt*
+
+## Description
+Originally from [Eat Sleep Wild](https://eatsleepwild.com/the-best-homemade-energy-bars-for-hiking-and-backpacking/)
+
+## Ingredients
+- 360g mashed banana (about 3 large)
+- 1 tsp vanilla extract
+- 200g porridge oats
+- 90g goji berries
+- 50g walnuts
+- 30g chia seeds
+- 80g pepita seeds
+- 60g sliced almonds
+- 25g ground flax seed meal
+- 1 tsp cinnamon
+- 1/4 tsp fine sea salt
+
+## Instructions
+1. Preheat oven to 180°C / 350°F. Grease and line 9″ x 13″ dish with parchment.
+2. Mash banana, stir in vanilla. Add remaining ingredients, mix well.
+3. Let sit 5-10 minutes for chia to absorb moisture.
+4. Press into dish with wet hands until compacted.
+5. Bake 22-26 minutes until firm and golden on edges.
+6. Cool 10 minutes, lift out, cool completely, slice into bars.
+7. Store in fridge for a week or freezer for 4-6 weeks.