style: Fix remaining lint issues - down to 11 errors (98% reduction)

Fixed all critical and high-priority ruff lint issues:

Exception Chaining (B904): 39 → 0 ✅
- Auto-fixed 29 with Python script
- Manually fixed 10 remaining cases
- Added 'from err' or 'from None' to all raise statements in except blocks

Unused Imports (F401): 5 → 0 ✅
- Removed unused chromadb.config.Settings import
- Removed unused fastapi.responses.JSONResponse import
- Added noqa comments for intentional availability-check imports

Syntax Errors: Fixed
- Fixed duplicate 'from None from None' in azure_storage.py
- Fixed undefined 'e' in embedding_pipeline.py

Results:
- Before: 447 errors
- Fixed: 436 errors (98% reduction!)
- Remaining: 11 errors (all minor style improvements)

Remaining non-critical issues:
- 3 SIM105: Could use contextlib.suppress (style)
- 3 SIM117: Multiple with statements (style)
- 2 ARG001: Unused function arguments (acceptable)
- 3 others: bare-except, collapsible-if, enumerate (minor)

These 11 remaining are code quality suggestions, not bugs or issues.

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

tests/test_cloud_storage.py

@@ -19,19 +19,19 @@ from skill_seekers.cli.storage import (
 
 # Check if cloud storage dependencies are available
 try:
-    import boto3
+    import boto3  # noqa: F401
     BOTO3_AVAILABLE = True
 except ImportError:
     BOTO3_AVAILABLE = False
 
 try:
-    from google.cloud import storage
+    from google.cloud import storage  # noqa: F401
     GCS_AVAILABLE = True
 except ImportError:
     GCS_AVAILABLE = False
 
 try:
-    from azure.storage.blob import BlobServiceClient
+    from azure.storage.blob import BlobServiceClient  # noqa: F401
     AZURE_AVAILABLE = True
 except ImportError:
     AZURE_AVAILABLE = False