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)

routes/waitlist_routes.py

@@ -0,0 +1,98 @@
+"""
+Waitlist / email-capture routes for the marketing landing page.
+
+Public endpoint: POST /api/v1/waitlist (no auth) — deduplicated by email,
+persisted in data/waitlist.json (same JSON-file pattern as provider settings).
+"""
+
+import json
+import logging
+import threading
+from datetime import datetime, timezone
+from typing import List, Optional
+
+from fastapi import APIRouter
+from fastapi.responses import JSONResponse
+from pydantic import BaseModel, EmailStr
+
+from config import config
+
+logger = logging.getLogger(__name__)
+
+router = APIRouter(prefix="/api/v1/waitlist", tags=["Waitlist"])
+
+WAITLIST_FILE = config.BASE_DIR / "data" / "waitlist.json"
+_write_lock = threading.Lock()
+
+
+class WaitlistEntry(BaseModel):
+    email: EmailStr
+    interest: Optional[str] = None
+
+
+def _load_waitlist() -> List[dict]:
+    if not WAITLIST_FILE.exists():
+        return []
+    try:
+        with open(WAITLIST_FILE, encoding="utf-8") as f:
+            data = json.load(f)
+        return data if isinstance(data, list) else []
+    except Exception as e:
+        logger.warning(f"Failed to load waitlist: {e}")
+        return []
+
+
+def _save_waitlist(entries: List[dict]) -> None:
+    WAITLIST_FILE.parent.mkdir(parents=True, exist_ok=True)
+    with open(WAITLIST_FILE, "w", encoding="utf-8") as f:
+        json.dump(entries, f, indent=2)
+
+
+@router.post("", status_code=201, summary="Join the waitlist")
+async def join_waitlist(entry: WaitlistEntry):
+    email = entry.email.lower().strip()
+    now = datetime.now(timezone.utc).isoformat()
+
+    with _write_lock:
+        entries = _load_waitlist()
+        for existing in entries:
+            if existing.get("email", "").lower() == email:
+                existing["updated_at"] = now
+                if entry.interest:
+                    existing["interest"] = entry.interest
+                _save_waitlist(entries)
+                logger.info(f"Waitlist rejoin: {email}")
+                return JSONResponse(
+                    status_code=200,
+                    content={
+                        "data": {"email": email, "status": "already_joined"},
+                        "message": "You are already on the list.",
+                    },
+                )
+
+        entries.append(
+            {
+                "email": email,
+                "interest": entry.interest,
+                "joined_at": now,
+                "updated_at": now,
+            }
+        )
+        _save_waitlist(entries)
+        logger.info(f"Waitlist join: {email} (total={len(entries)})")
+
+    return JSONResponse(
+        status_code=201,
+        content={
+            "data": {"email": email, "status": "joined"},
+            "message": "Welcome aboard!",
+        },
+    )
+
+
+@router.get("/count", summary="Waitlist count")
+async def waitlist_count():
+    return JSONResponse(
+        status_code=200,
+        content={"data": {"count": len(_load_waitlist())}},
+    )