Check translation contracts offline, add Swedish to the installer and enable the website languages

- Offline checks for terminal and website catalogs reject translations that change commands, paths, identifiers or placeholders
- Terminal and documentation texts that broke those contracts are corrected in every language
- Swedish can be chosen in the stable and beta installers
- The website routes, language switcher and exported pages cover the eight languages, with the shared website texts in each of them
- Website documentation translations are generated only when requested
- From PR #475 by @jcastro

.github/scripts/check_terminal_catalogs.py

@@ -0,0 +1,77 @@
+#!/usr/bin/env python3
+"""Check active terminal translations offline, without generating any text.
+
+Validates formatting fields and literal commands/identifiers. Missing values
+can retain English fallback; --require-complete makes them errors. This does
+not establish the accuracy or fluency of the translated prose.
+"""
+from __future__ import annotations
+
+import argparse
+from pathlib import Path
+import re
+
+from build_translation_cache import (
+    DEFAULT_LANGUAGES, STRUCTURAL_LITERAL_RE, extract_catalog_texts,
+    extract_python_texts, extract_translate_texts,
+)
+from build_web_docs_i18n import read_json, validate_contract
+
+
+def active_sources(root: Path) -> list[str]:
+    # Match build-translation-cache.yml, including launchers outside scripts/.
+    extras = [root / name for name in ('menu', 'install_proxmenux.sh', 'install_proxmenux_beta.sh')]
+    texts = extract_translate_texts(root / 'scripts', extras)
+    texts += extract_translate_texts(root / 'oci/remote')
+    texts += extract_python_texts([root / 'scripts', root / 'oci/src', root / 'oci/remote'])
+    texts += extract_catalog_texts([root / 'oci/catalog'])
+    return sorted({text for text in texts if '$' not in text and '`' not in text})
+
+
+def validate_message(source: str, target: str, *, title_separator: bool = False) -> None:
+    validate_contract(source, target)
+    for match in STRUCTURAL_LITERAL_RE.finditer(source):
+        literal = match.group()
+        # A page title may replace its decorative separator with a dash.
+        # In command examples, a pipe remains a shell operator.
+        if title_separator and literal == '|':
+            continue
+        # DNS hostnames are case-insensitive. Paths, field names and command
+        # names are not, so do not case-fold those to hide a broken example.
+        is_hostname = re.fullmatch(r'[A-Za-z0-9.-]+\.(?:com|org|net|io)', literal)
+        if literal not in target and not (is_hostname and literal.casefold() in target.casefold()):
+            raise ValueError(f'literal command or identifier changed: {literal}')
+
+
+def main() -> int:
+    parser = argparse.ArgumentParser(description=__doc__)
+    parser.add_argument('--root', type=Path, default=Path('.'))
+    parser.add_argument('--languages', default=','.join(DEFAULT_LANGUAGES))
+    parser.add_argument('--require-complete', action='store_true')
+    args = parser.parse_args()
+    root = args.root.resolve()
+    texts = active_sources(root)
+    errors = 0
+    for language in args.languages.split(','):
+        if language not in DEFAULT_LANGUAGES:
+            parser.error(f'Unsupported locale: {language}')
+        catalog = read_json(root / 'lang' / f'{language}.json') or {}
+        missing = 0
+        for source in texts:
+            target = catalog.get(source)
+            if not isinstance(target, str) or not target.strip():
+                missing += 1
+                continue
+            try:
+                validate_message(source, target)
+            except ValueError as error:
+                print(f'[{language}] {source!r}: {error}')
+                errors += 1
+        print(f'[{language}] active={len(texts)} missing={missing}')
+        if args.require_complete and missing:
+            errors += 1
+    return 1 if errors else 0
+
+
+if __name__ == '__main__':
+    raise SystemExit(main())