feat(error-handling): add network error differentiation, retry, and REST API detection (C.5)

WordPress client improvements:
- Add ConnectionError exception for network-level failures
- Differentiate DNS, SSL, timeout, and connection refused errors
- Add retry with exponential backoff for transient errors (502, 503, 504, 429)
- Auth/config errors are never retried
- Add request timeout (30s default)

Health check improvements:
- Detect REST API disabled (403/404 on /wp-json)
- Classify errors by type: dns_failure, ssl_error, timeout, connection_refused

Bare except cleanup:
- Replaced all bare except: with except Exception: across 12 files

Tests: 303 passed (13 new tests for error handling)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

core/oauth/token_manager.py

@@ -241,8 +241,8 @@ class TokenManager:
             try:
                 old_payload = self.validate_access_token(token_data.access_token)
                 scope = old_payload.get("scope", "read")
-            except:
-                pass  # Old token might be expired, use default
+            except Exception:
+                pass  # Old token might be expired, use default scope
 
         # Generate new tokens
         new_access_token = self.generate_access_token(