feat: add cameleer-license-minter dependency and V002 migration

Adds Ed25519 license minting library, signing_keys table,
renames tiers (LOW→STARTER, MID→TEAM, HIGH→BUSINESS, BUSINESS→ENTERPRISE),
adds label + grace_period_days to licenses, drops features column.

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

pom.xml

@@ -100,6 +100,13 @@
             <version>3.4.1</version>
         </dependency>
 
+        <!-- License Minter (Ed25519 signing) -->
+        <dependency>
+            <groupId>com.cameleer</groupId>
+            <artifactId>cameleer-license-minter</artifactId>
+            <version>1.0-SNAPSHOT</version>
+        </dependency>
+
         <!-- Mail (for password-reset security notification) -->
         <dependency>
             <groupId>org.springframework.boot</groupId>