Sync versions to 2.1.0 and add sister project references

- Updated all platform versions to 2.1.0 (Java, Python, Maven)
- Added comprehensive sister projects section to README
- Links to nhtsa-recall-lookup and dtc-database repos
- Describes complete diagnostic workflow integration

Author: Wal33D

README.md

@@ -10,6 +10,16 @@
 
 World-class VIN decoder with comprehensive offline database (2,015+ WMI codes) and NHTSA vPIC API integration
 
+## Sister Projects
+
+Part of the NHTSA automotive diagnostic toolkit:
+
+- **[nhtsa-vin-decoder](https://github.com/Wal33D/nhtsa-vin-decoder)** - This project (VIN decoder)
+- **[nhtsa-recall-lookup](https://github.com/Wal33D/nhtsa-recall-lookup)** - Look up safety recalls using decoded vehicle info
+- **[dtc-database](https://github.com/Wal33D/dtc-database)** - Comprehensive OBD-II diagnostic trouble code database
+
+**Workflow:** Decode VIN → Get vehicle info → Look up recalls → Decode diagnostic codes
+
 ## ⚡ Quick Start
 
 ### Java - Offline Mode (No Internet Required)

build.gradle

@@ -3,7 +3,7 @@ plugins {
 }
 
 group = 'io.github.vindecoder'
-version = '0.1.0'
+version = '2.1.0'
 
 java {
     sourceCompatibility = JavaVersion.VERSION_17

pom.xml

@@ -6,7 +6,7 @@
 
     <groupId>io.github.wal33d</groupId>
     <artifactId>nhtsa-vin-decoder</artifactId>
-    <version>0.1.0</version>
+    <version>2.1.0</version>
     <packaging>jar</packaging>
 
     <name>NHTSA VIN Decoder</name>

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "setuptools.build_meta"
 
 [project]
 name = "nhtsa-vin-decoder"
-version = "0.1.0"
+version = "2.1.0"
 description = "World-class VIN decoder with comprehensive offline database (2,015+ WMI codes) and NHTSA vPIC API integration"
 readme = "README.md"
 authors = [