Download agency data at runtime instead of committing to repo

- Add runtime download from civictechsweden/myndighetsdata
- Use myndighetsdata_fallback.json as backup when download fails
- Remove agencies.json from git, add to .gitignore
- Convert handlingar.json format to expected structure

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Sonnet 4.5 <noreply@anthropic.com>

Author: marcarl

.gitignore

@@ -23,4 +23,7 @@ output/
 # Data directory contains source files committed to git:
 # - data/sfs_json/     = Käll-JSON från API
 # - data/md-markers/   = Markdown med selex-taggar
-# (nothing to ignore here, committed to git + backed up to R2)
+# (nothing to ignore here, committed to git + backed up to R2)
+
+# Ignore downloaded agencies data (fetched at runtime)
+data/agencies.json