feat: add patchNodeField operation for surgical string edits (v2.46.0) (#698)

Add dedicated `patchNodeField` operation to `n8n_update_partial_workflow`
for surgical find/replace edits in node string fields. Strict alternative
to the existing `__patch_find_replace` in updateNode — errors on not-found,
detects ambiguous matches, supports replaceAll and regex flags.

Security hardening:
- Prototype pollution protection in setNestedProperty/getNestedProperty
- ReDoS protection rejecting unsafe regex patterns (nested quantifiers)
- Resource limits: max 50 patches, 500-char regex, 512KB field size

Fixes #696

Conceived by Romuald Członkowski - https://www.aiadvisors.pl/en

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

dist/services/workflow-diff-engine.d.ts

@@ -14,6 +14,7 @@ export declare class WorkflowDiffEngine {
     private validateAddNode;
     private validateRemoveNode;
     private validateUpdateNode;
+    private validatePatchNodeField;
     private validateMoveNode;
     private validateToggleNode;
     private validateAddConnection;
@@ -22,6 +23,7 @@ export declare class WorkflowDiffEngine {
     private applyAddNode;
     private applyRemoveNode;
     private applyUpdateNode;
+    private applyPatchNodeField;
     private applyMoveNode;
     private applyEnableNode;
     private applyDisableNode;