feat: production deployment - full update with providers, admin, glossaries, pricing, tests

Major changes across backend, frontend, infrastructure:
- Provider system with model selection (Google, DeepL, OpenAI, Ollama, Google Cloud)
- Admin panel: user management, pricing, settings
- Glossary system with CSV import/export
- Subscription and tier quota management
- Security hardening (rate limiting, API key auth, path traversal fixes)
- Docker compose for dev, prod, and IONOS deployment
- Alembic migrations for new tables
- Frontend: dashboard, pricing page, landing page, i18n (en/fr)
- Test suite and verification scripts

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

tests/test_story_2_13_validation.py

@@ -0,0 +1,57 @@
+import pytest
+from fastapi.testclient import TestClient
+from main import app
+from routes.translate_routes import TranslateEndpointError
+
+client = TestClient(app)
+
+def test_validate_unsupported_extension():
+    # Test with .txt file
+    files = {"file": ("test.txt", b"some text content", "text/plain")}
+    response = client.post(
+        "/api/v1/translate",
+        files=files,
+        data={"target_lang": "fr"}
+    )
+    assert response.status_code == 400
+    assert response.json()["error"] == "INVALID_FORMAT"
+    # Updated message to French
+    assert "Formats acceptes" in response.json()["message"]
+
+def test_validate_invalid_magic_bytes():
+    # Test with .docx extension but invalid content (should trigger CORRUPTED_FILE)
+    files = {"file": ("test.docx", b"not a zip file", "application/vnd.openxmlformats-officedocument.wordprocessingml.document")}
+    response = client.post(
+        "/api/v1/translate",
+        files=files,
+        data={"target_lang": "fr"}
+    )
+    assert response.status_code == 400
+    assert response.json()["error"] == "CORRUPTED_FILE"
+    assert "corrompu" in response.json()["message"]
+    
+def test_validate_valid_file_header():
+    # Test with a minimal valid-looking zip (Office files are ZIPs)
+    # FileValidator checks for b"PK\x03\x04"
+    files = {"file": ("test.docx", b"PK\x03\x04" + b"\x00" * 20, "application/vnd.openxmlformats-officedocument.wordprocessingml.document")}
+    response = client.post(
+        "/api/v1/translate",
+        files=files,
+        data={"target_lang": "fr"}
+    )
+    # Should be 202 (Accepted) if validation passes
+    assert response.status_code == 202
+    assert response.json()["data"]["status"] == "processing"
+
+def test_validate_too_large_file():
+    # Test with file larger than 50MB
+    large_content = b"PK\x03\x04" + b"0" * (51 * 1024 * 1024)
+    files = {"file": ("large.docx", large_content, "application/vnd.openxmlformats-officedocument.wordprocessingml.document")}
+    response = client.post(
+        "/api/v1/translate",
+        files=files,
+        data={"target_lang": "fr"}
+    )
+    assert response.status_code == 413
+    assert response.json()["error"] == "FILE_TOO_LARGE"
+    assert "volumineux" in response.json()["message"]