Initial version of fail2ban-webui

Web interface to view, ban and unban fail2ban IPs on several hosts via
SSH, generalised from the private f2b-web tool.

- Web UI (Flask/Waitress): hosts.yaml, local/OIDC/proxy authentication,
  English/German UI, origin map, optional Loki/Grafana/GeoIP, CLI helpers
- Agent f2b-webctl with install.sh/uninstall.sh (dedicated user + sudo,
  from= restriction, protected networks, manual jail)
- Hardened Docker image, examples, documentation, smoke test, testbed

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

app/webui/i18n.py

@@ -0,0 +1,45 @@
+"""Translations: one JSON file per language in webui/locales/ (e.g. en.json, de.json).
+
+A new language only needs a new file; "_name" is the label shown in the dropdown.
+Missing keys fall back to English.
+"""
+import json
+import os
+
+DIR = os.path.join(os.path.dirname(__file__), "locales")
+FALLBACK = "en"
+LANGS = {}
+
+
+def load():
+    LANGS.clear()
+    for fname in sorted(os.listdir(DIR)):
+        if fname.endswith(".json"):
+            with open(os.path.join(DIR, fname), encoding="utf-8") as fh:
+                LANGS[fname[:-5]] = json.load(fh)
+
+
+def pick(cookie_value, default):
+    if cookie_value in LANGS:
+        return cookie_value
+    return default if default in LANGS else FALLBACK
+
+
+def catalog(lang):
+    """Full dictionary for the browser, English as base."""
+    return {**LANGS.get(FALLBACK, {}), **LANGS.get(lang, {})}
+
+
+def translate(lang, key, **params):
+    text = LANGS.get(lang, {}).get(key) or LANGS.get(FALLBACK, {}).get(key) or key
+    try:
+        return text.format(**params) if params else text
+    except (KeyError, IndexError, ValueError):
+        return text
+
+
+def languages():
+    return [(code, data.get("_name", code)) for code, data in sorted(LANGS.items())]
+
+
+load()