feat(mcp-docugen): Task 1-3 config, models, auth middleware

- Settings con Pydantic Settings, validazione env obbligatori
- Shared models: TemplateVariable/Frontmatter, ImageVariable, TokenUsage, GenerationResult, TemplateSummary, TemplateAsset
- ApiKeyAuthMiddleware Bearer token con exempt paths

19 test, tutti passed.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

services/mcp-docugen/tests/unit/test_config.py

@@ -0,0 +1,44 @@
+import pytest
+from pydantic import ValidationError
+
+from mcp_docugen.config import Settings
+
+
+def test_settings_loads_from_env(monkeypatch, tmp_path):
+    monkeypatch.setenv("API_KEY", "test-api-key")
+    monkeypatch.setenv("OPENROUTER_API_KEY", "sk-or-test")
+    monkeypatch.setenv("PUBLIC_BASE_URL", "https://mcp.example.com")
+    monkeypatch.setenv("DATA_DIR", str(tmp_path))
+
+    settings = Settings()
+
+    assert settings.api_key == "test-api-key"
+    assert settings.openrouter_api_key == "sk-or-test"
+    assert settings.public_base_url == "https://mcp.example.com"
+    assert settings.data_dir == tmp_path
+    assert settings.llm_model_default == "anthropic/claude-sonnet-4"
+    assert settings.asset_ttl_days == 30
+    assert settings.max_image_size_mb == 10
+    assert settings.llm_timeout_seconds == 60
+    assert settings.openrouter_base_url == "https://openrouter.ai/api/v1"
+
+
+def test_settings_missing_required_fails(monkeypatch, tmp_path):
+    monkeypatch.delenv("API_KEY", raising=False)
+    monkeypatch.delenv("OPENROUTER_API_KEY", raising=False)
+    monkeypatch.delenv("PUBLIC_BASE_URL", raising=False)
+    monkeypatch.setenv("DATA_DIR", str(tmp_path))
+
+    with pytest.raises(ValidationError):
+        Settings(_env_file=None)
+
+
+def test_public_base_url_strips_trailing_slash(monkeypatch, tmp_path):
+    monkeypatch.setenv("API_KEY", "k-with-long-enough")
+    monkeypatch.setenv("OPENROUTER_API_KEY", "sk-long-enough")
+    monkeypatch.setenv("PUBLIC_BASE_URL", "https://mcp.example.com/")
+    monkeypatch.setenv("DATA_DIR", str(tmp_path))
+
+    settings = Settings()
+
+    assert settings.public_base_url == "https://mcp.example.com"