feat: pzmm conflict detection + content-type categorization

- mod_files manifest table populated at parse time
- POST /api/conflicts endpoint
- mod_types fingerprinting feeds derive_category
- DD filelist regex broadened to cover conflict-eligible exts
- media/maps/<*>/* excluded from manifest (per-mod namespaced,
  no conflict value, can be tens of MB per mod)

Plan: docs/plans/2026-05-04-pzmm-conflict-and-typing.md

.gitignore

@@ -20,6 +20,9 @@ __pycache__/
 *.bak
 *.bak-*
 
+# Operational DB dumps (pg_dump output kept locally for rollback)
+backups/
+
 # Editor / IDE / OS artifacts
 *.swp
 *.swo