chore: keep host/client specifics out of the tree (env & config)

Showroom-safe: the tree no longer carries internal hosts, IPs, ports,
personal names, client domains or client file names. Behaviour is
unchanged and now supplied per deployment.

- catalog: hardcoded mail-org / project classifiers become a YAML-driven
  Classifier (OO_CATALOG_CONFIG or --config); neutral default classifies
  nothing as work. New catalog/classify.go + example + tests.
- storage_fallback: drop the baked-in MinIO endpoint IP; require
  MINIO_ENDPOINT (+ keys) from the env.
- kontolink: build DocEditor links from $ONLYOFFICE_URL instead of a
  hardcoded portal host; kontoblatt: no client file id in the output name.
- oo: load .env CLI-wide (bootstrap.LoadEnv in execute) so
  non-authenticating commands (catalog scans) also see config.
- genericize comments/docs/fixtures (AGENTS, README, .env.example,
  crm-associations, catalog tests, ES/pdfattach tests, mails).

files.go

@@ -278,7 +278,7 @@ func (c *Client) RenameFile(ctx context.Context, fileID, newTitle string) (*File
 
 // DeleteFiles permanently deletes files by numeric id (Documents module).
 // Uses per-file DELETE (DeleteDavItems); fileops/delete returns 200 on some
-// portals (e.g. produktor.io) without removing the file.
+// portals without actually removing the file.
 //
 // Deprecated: use FileStore.Delete via Client.Files()/Client.FileStore.
 func (c *Client) DeleteFiles(ctx context.Context, fileIDs []int) error {