ci: enable ruff linting and pytest in CI pipeline

Uncomment the ruff check and pytest steps in the Gitea Actions build
workflow so that linting violations and test failures block image builds.
Fix all pre-existing ruff violations (E402 import ordering in analyzer.py,
F821 undefined name in api.py, I001 unsorted imports in test files, F401
unused import in test_rate_limit.py).

Closes leeworks-agents/SPARC#1559
Closes leeworks-agents/SPARC#1560

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

SPARC/analyzer.py

@@ -10,13 +10,13 @@ from concurrent.futures import ThreadPoolExecutor, as_completed
 from typing import Callable
 
 from SPARC import config
-
-logger = logging.getLogger(__name__)
 from SPARC.database import DatabaseClient
 from SPARC.llm import LLMAnalyzer
 from SPARC.serp_api import SERP
 from SPARC.types import BatchAnalysisResult, CompanyAnalysisResult, Patent, Patents
 
+logger = logging.getLogger(__name__)
+
 
 class CompanyAnalyzer:
     """Orchestrates end-to-end company performance analysis via patents."""

SPARC/api.py

@@ -3,9 +3,14 @@
 Provides REST API endpoints for analyzing company patent portfolios.
 """
 
+from __future__ import annotations
+
 from contextlib import asynccontextmanager
 from datetime import datetime
-from typing import Annotated, List
+from typing import TYPE_CHECKING, Annotated, List
+
+if TYPE_CHECKING:
+    from SPARC.database import DatabaseClient
 
 from fastapi import BackgroundTasks, Depends, FastAPI, HTTPException, Query, Request
 from fastapi.middleware.cors import CORSMiddleware
@@ -653,7 +658,6 @@ async def export_company_pdf(
         PDF file download
     """
     import io
-    import textwrap
 
     from reportlab.lib import colors
     from reportlab.lib.pagesizes import letter