feat(build): fix lookaside cache fallback and organize repository structure

- Add fallback to official CentOS Stream lookaside cache in SCM get-sources script
- Update documentation to reflect CentOS-style structured repositories on cs10-repo
- Update project journal with progress and decisions

Co-developed-by: Gemini AI <renich+gemini@woralelandia.com>
Signed-off-by: Rénich Bon Ćirić <renich@woralelandia.com>

roles/kojid/files/mxos-get-sources.bash

@@ -36,8 +36,14 @@ while read -r alg filename_part eq hash; do
     # URL: SURL/rpms/PKGNAME/FILENAME/ALGO/HASH/FILENAME
     url="$SURL/rpms/$PKGNAME/$filename/$alg_lower/$hash/$filename"
     
-    echo "Downloading $filename from $url"
-    curl -L --fail --retry 5 -o "$filename" "$url"
+    echo "Downloading $filename from local lookaside: $url"
+    if curl -L --fail --retry 3 -o "$filename" "$url"; then
+        echo "Successfully downloaded $filename from local lookaside."
+    else
+        upstream_url="https://sources.stream.centos.org/sources/rpms/$PKGNAME/$filename/$alg_lower/$hash/$filename"
+        echo "Local download failed. Trying upstream CentOS Stream lookaside: $upstream_url"
+        curl -L --fail --retry 5 -o "$filename" "$upstream_url"
+    fi
     
     # Verify hash (optional but good)
     echo "$hash  $filename" | sha512sum -c -