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>

plugins/wordpress/wp_cli.py

@@ -599,7 +599,7 @@ class WPCLIManager:
                     size_str = f"{size_bytes / (1024 * 1024):.1f} MB"
             else:
                 size_str = "unknown"
-        except:
+        except (ValueError, IndexError, OSError):
             size_str = "unknown"
 
         return {
@@ -1198,7 +1198,7 @@ class WPCLIManager:
                     site_cmd = "core version"
                     version_result = await self._execute_wp_cli(site_cmd)
                     current_version = version_result.get("message", "unknown").strip()
-                except:
+                except Exception:
                     current_version = "unknown"
 
                 return {
@@ -1220,7 +1220,7 @@ class WPCLIManager:
             try:
                 version_result = await self._execute_wp_cli("core version")
                 old_version = version_result.get("message", "unknown").strip()
-            except:
+            except Exception:
                 old_version = "unknown"
 
             # Execute update (long timeout for downloads)
@@ -1230,7 +1230,7 @@ class WPCLIManager:
             try:
                 version_result = await self._execute_wp_cli("core version")
                 new_version = version_result.get("message", "unknown").strip()
-            except:
+            except Exception:
                 new_version = "unknown"
 
             # Determine update type