feat: v2 Vue3 frontend + multiple optimizations

- New Vue 3 + Vite frontend at /v2/ (OLED dark theme, Fira Sans/Code)
- Date selector: support day/week/month range (backend unchanged)
- SSE auto-reconnect (up to 3 retries)
- Visibility polling pause (dashboard pauses when tab hidden)
- Friendly Chinese HTTP error messages
- Cancel task with confirmation in Dashboard
- Split AiWorkflowService (1700->845 lines):
  - AiApiService: AI API calls + streaming
  - ExcelExportService: POI Excel generation
- Dockerfile: 3-stage build (Node frontend -> Maven -> JRE)
- WebApplication.java: System.out -> Logger
- .gitignore: v2 build output, backup dirs

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/main/java/com/svnlog/web/dto/SvnVersionRangeRequest.java

@@ -1,7 +1,6 @@
 package com.svnlog.web.dto;
 
 import javax.validation.constraints.NotBlank;
-import javax.validation.constraints.NotNull;
 
 public class SvnVersionRangeRequest {
 
@@ -12,11 +11,16 @@ public class SvnVersionRangeRequest {
 
     private String password;
 
-    @NotNull
     private Integer year;
 
-    @NotNull
     private Integer month;
+
+    private String rangeType;
+
+    private String date;
+
+    private String week;
+
     private String clientTraceId;
 
     public String getPresetId() {
@@ -59,6 +63,30 @@ public class SvnVersionRangeRequest {
         this.month = month;
     }
 
+    public String getRangeType() {
+        return rangeType;
+    }
+
+    public void setRangeType(String rangeType) {
+        this.rangeType = rangeType;
+    }
+
+    public String getDate() {
+        return date;
+    }
+
+    public void setDate(String date) {
+        this.date = date;
+    }
+
+    public String getWeek() {
+        return week;
+    }
+
+    public void setWeek(String week) {
+        this.week = week;
+    }
+
     public String getClientTraceId() {
         return clientTraceId;
     }