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/health.py

@@ -553,6 +553,7 @@ class HealthMonitor:
 
     async def _basic_http_health_check(self, url: str | None, project_id: str) -> dict[str, Any]:
         """Basic HTTP health check as a last-resort fallback."""
+
         import aiohttp
 
         if not url:
@@ -568,8 +569,27 @@ class HealthMonitor:
                         "status_code": resp.status,
                         "message": f"HTTP {resp.status} from {url}",
                     }
+        except TimeoutError:
+            return {
+                "healthy": False,
+                "error_type": "timeout",
+                "message": f"Site at {url} did not respond within 10 seconds.",
+            }
+        except aiohttp.ClientConnectorDNSError:
+            host = url.split("://")[-1].split("/")[0]
+            return {
+                "healthy": False,
+                "error_type": "dns_failure",
+                "message": f"DNS resolution failed for '{host}'. Check the URL.",
+            }
+        except aiohttp.ClientConnectorError:
+            return {
+                "healthy": False,
+                "error_type": "connection_refused",
+                "message": f"Cannot connect to {url}. Server unreachable.",
+            }
         except Exception as e:
-            return {"healthy": False, "message": f"Connection failed: {e}"}
+            return {"healthy": False, "error_type": "unknown", "message": f"Connection failed: {e}"}
 
     async def check_all_projects_health(self, include_metrics: bool = True) -> dict[str, Any]:
         """