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).

catalog/mbox_test.go

@@ -10,22 +10,22 @@ func TestParseMboxHeaderEmails(t *testing.T) {
 	dir := t.TempDir()
 	path := filepath.Join(dir, "INBOX")
 	body := `From - Mon Jul 1 00:00:00 2016
-From: Axel Schaefer <axel.schaefer@wheregroup.com>
-To: Andriy Oblivantsev <andriy.oblivantsev@wheregroup.com>
+From: Alice Smith <alice.smith@acme.example>
+To: Bob Jones <bob.jones@acme.example>
 Cc: noreply@example.com, client@stadt-example.de
 Subject: test
 
 Body line ignored
 From - Mon Jul 2 00:00:00 2016
-From: Someone <paul.schmidt@wheregroup.com>
-To: list@wheregroup.com
+From: Someone <paul.schmidt@acme.example>
+To: list@acme.example
 
 more body
 `
 	if err := os.WriteFile(path, []byte(body), 0o644); err != nil {
 		t.Fatal(err)
 	}
-	ents, err := parseMboxHeaderEmails(path)
+	ents, err := parseMboxHeaderEmails(path, DefaultClassifier())
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -35,7 +35,7 @@ more body
 			got[e.Emails[0]] = true
 		}
 	}
-	if !got["axel.schaefer@wheregroup.com"] || !got["andriy.oblivantsev@wheregroup.com"] {
+	if !got["alice.smith@acme.example"] || !got["bob.jones@acme.example"] {
 		t.Fatalf("%v", got)
 	}
 	if got["noreply@example.com"] {
@@ -53,7 +53,7 @@ func TestScanThunderbirdRootOptsMbox(t *testing.T) {
 		t.Fatal(err)
 	}
 	if err := os.WriteFile(filepath.Join(imap, "INBOX"), []byte(
-		"From - x\nFrom: a@wheregroup.com\nTo: b@wheregroup.com\n\nbody\n",
+		"From - x\nFrom: a@acme.example\nTo: b@acme.example\n\nbody\n",
 	), 0o644); err != nil {
 		t.Fatal(err)
 	}