feat(translation): quality pipeline overhaul + new features (audit 2026-08-29)

Translation quality & format preservation:
- Word: merge adjacent same-format runs into one unit (sentence-level
  coherence like inline-tag handling); translate comments/balloons;
  dedupe textbox collection (was translated twice); RTL no longer
  overrides center/justify alignment; CJK/Arabic font hints (eastAsia/cs)
- PPTX: chart translations now actually reach the output file
  (ChartPart.blob is read-only — rewrite chart XML in the saved ZIP);
  CJK typeface hints (a:ea)
- Excel: sheet renames no longer break references — rewrite cell
  formulas (3D/quoted), defined names, data validations, cond. formats
- PDF: bold/italic honored (hebo/heit/hebi); table cells never merge;
  unchanged blocks left untouched (typography preserved, fixes duplicate
  hyperlinks); attempted/changed stats + route gate now cover PDF;
  CJK font paths; scanned PDFs via Mistral OCR (detection + admin settings)

Features:
- formality param (formal/informal) + automatic regional-variant prompts
- output_mode=bilingual docx (source above translation)
- per-user translation memory on Redis (falls back to LRU), context-hashed
- QA report + 0-100 confidence score in job status; L0 on by default
- OpenAI-compatible providers: whole chunk in ONE numbered-JSON request
  (~15x fewer calls) with per-item fallback; base prompt always present
  (custom prompt no longer replaces translation instructions)

Infra & marketing alignment:
- plan-based engine gating + vision gating (closes paid-engine leak);
  /providers/available filtered per plan; 107 languages exposed
- zh-CN/zh-TW validation fixed; libmagic disabled on Windows (native crash)
- admin: Mistral OCR settings + engine status dashboard; httpx<0.28 pin
  (TestClient breakage); Prometheus test fixture fixed
- marketing docs aligned with code (PDF+OCR, retention, engines, pricing)
- security: .env.ionos/.env.production/provider_settings.json removed

Tests: 1173 passed / 0 failed (6 network tests deselected: free Google
endpoint temporarily blocked from this machine)

tests/test_translation_metadata_integration.py

@@ -40,7 +40,11 @@ async def test_translate_endpoint_triggers_tracking(client):
     with patch(
         "routes.translate_routes.storage_tracker.track_file", new_callable=AsyncMock
     ) as mock_track:
-        with patch("routes.translate_routes.file_validator.validate_async") as mock_val:
+        # The upload write is mocked below, so no real archive exists on
+        # disk: neutralize the zip safety check for this test.
+        with patch(
+            "routes.translate_routes.file_validator.validate_async"
+        ) as mock_val, patch("routes.translate_routes.validate_zip_safety"):
             mock_val.return_value.is_valid = True
             mock_val.return_value.data = {"extension": ".docx", "size_bytes": 500}
 
@@ -88,7 +92,10 @@ async def test_translate_endpoint_triggers_tracking(client):
 async def test_translate_endpoint_handles_hash_failure(client):
     app.dependency_overrides[get_authenticated_user] = mock_auth
 
-    with patch("routes.translate_routes.file_validator.validate_async") as mock_val:
+    # No real archive exists on disk (save is mocked): skip the zip check.
+    with patch(
+        "routes.translate_routes.file_validator.validate_async"
+    ) as mock_val, patch("routes.translate_routes.validate_zip_safety"):
         mock_val.return_value.is_valid = True
         mock_val.return_value.data = {"extension": ".docx", "size_bytes": 500}