refactor: modularize post-install setup script

Break down monolithic script into focused components:
- 00-system-prep.sh: system updates and Flathub
- 01-package-install.sh: system packages and Flatpaks
- 02-dev-tools-setup.sh: Neovim, fonts, shell tools
- 03-fedora-dotnet-setup.sh: .NET development environment
- 04-config-symlinks.sh: dotfile symlinking

Fixes:
- Use rpm -q for accurate package checks
- Dynamic Fedora version detection
- Replace neofetch with fastfetch
- Correct dotfile names (aliases.zsh, commit-conventions.txt)

scripts/00-system-prep.sh

@@ -0,0 +1,34 @@
+#!/bin/bash
+
+# 00-system-prep.sh
+# Updates system and sets up Flathub.
+# Relies on DISTRO and PACKAGE_MANAGER being set by the caller.
+
+echo "--- Starting System Preparation ---"
+
+if [ -z "$DISTRO" ] || [ -z "$PACKAGE_MANAGER" ]; then
+    echo "ERROR: DISTRO and PACKAGE_MANAGER must be set in the environment."
+    exit 1
+fi
+
+# Update system before installing packages
+echo "Updating system packages..."
+if [ "$PACKAGE_MANAGER" == "dnf" ]; then
+    sudo dnf update -y && sudo dnf upgrade -y
+elif [ "$PACKAGE_MANAGER" == "apt" ]; then
+    sudo apt update && sudo apt upgrade -y
+else
+    echo "WARNING: Unknown package manager '$PACKAGE_MANAGER'. Skipping system update."
+fi
+
+# Setup Flatpak
+echo "Setting up Flathub repository..."
+if command -v flatpak &> /dev/null; then
+    flatpak remote-add --if-not-exists flathub https://dl.flathub.org/repo/flathub.flatpakrepo
+else
+    echo "WARNING: flatpak command not found. Skipping Flathub setup."
+    echo "Ensure Flatpak is installed via 01-package-install.sh or manually."
+fi
+
+echo "--- System Preparation Finished ---"
+