Fix CACHE_DIR default path mismatch across files

Changed default from /data/cache to ~/.artdag/cache for local runs.
Docker sets CACHE_DIR=/data/cache via environment variable.

Files updated:
- tasks/analyze.py
- tasks/orchestrate.py
- app/config.py

🤖 Generated with [Claude Code](https://claude.com/claude-code)

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

tasks/analyze.py

@@ -28,7 +28,7 @@ except ImportError:
 logger = logging.getLogger(__name__)
 
 # Cache directory for analysis results
-CACHE_DIR = Path(os.environ.get('CACHE_DIR', '/data/cache'))
+CACHE_DIR = Path(os.environ.get('CACHE_DIR', str(Path.home() / ".artdag" / "cache")))
 ANALYSIS_CACHE_DIR = CACHE_DIR / 'analysis'
 
 

tasks/orchestrate.py

@@ -42,7 +42,7 @@ from .execute import execute_step
 logger = logging.getLogger(__name__)
 
 # Cache directories
-CACHE_DIR = Path(os.environ.get('CACHE_DIR', '/data/cache'))
+CACHE_DIR = Path(os.environ.get('CACHE_DIR', str(Path.home() / ".artdag" / "cache")))
 ANALYSIS_CACHE_DIR = CACHE_DIR / 'analysis'
 PLAN_CACHE_DIR = CACHE_DIR / 'plans'