chore(deps): upgrade Netty (4.2), HikariCP (7) and JUnit (6) to latest major

Major-version upgrades of the three the previous bump deliberately held back.
Verified: clean compile, all 15 tests run green (surefire 3.5.2 drives the JUnit 6
platform fine — no extra launcher dep needed), and the shaded jar assembles.

- io.netty:netty-all            4.1.135.Final -> 4.2.15.Final
- com.zaxxer:HikariCP           6.3.3         -> 7.0.2
- org.junit.jupiter:junit-jupiter 5.14.4      -> 6.1.0

Notes:
- Stayed on Netty 4.2 (GA), not 5.0 which is still Alpha. No source changes
  needed; the channel ALLOCATOR is set explicitly so 4.2's new default adaptive
  allocator doesn't apply. NioEventLoopGroup is deprecated in 4.2 but still
  functions as before (left as-is to avoid an event-loop behavioural change).
  netty-all 4.2 pulls more transitive modules, so the fat jar grows (~20->32 MB).
- HikariCP 7.x baselines Java 17; our HikariConfig usage is unchanged.

Emulator/pom.xml

@@ -83,7 +83,7 @@
         <dependency>
             <groupId>io.netty</groupId>
             <artifactId>netty-all</artifactId>
-            <version>4.1.135.Final</version>
+            <version>4.2.15.Final</version>
         </dependency>
 
         <!-- GSON -->
@@ -113,7 +113,7 @@
         <dependency>
             <groupId>com.zaxxer</groupId>
             <artifactId>HikariCP</artifactId>
-            <version>6.3.3</version>
+            <version>7.0.2</version>
             <scope>compile</scope>
         </dependency>
 
@@ -190,7 +190,7 @@
         <dependency>
             <groupId>org.junit.jupiter</groupId>
             <artifactId>junit-jupiter</artifactId>
-            <version>5.14.4</version>
+            <version>6.1.0</version>
             <scope>test</scope>
         </dependency>
     </dependencies>