feat(skills): add Java Spring Boot skills

Adds 6 new skills for Java Spring Boot development:
- java-coding-standards: naming, immutability, Optional, streams
- springboot-patterns: REST API, service layer, caching, async
- springboot-tdd: JUnit 5, Mockito, MockMvc, Testcontainers
- springboot-security: Spring Security, validation, CSRF
- springboot-verification: Maven/Gradle build verification
- jpa-patterns: entity design, relationships

Thanks @examin!

skills/springboot-verification/SKILL.md

@@ -0,0 +1,100 @@
+---
+name: springboot-verification
+description: Verification loop for Spring Boot projects: build, static analysis, tests with coverage, security scans, and diff review before release or PR.
+---
+
+# Spring Boot Verification Loop
+
+Run before PRs, after major changes, and pre-deploy.
+
+## Phase 1: Build
+
+```bash
+mvn -T 4 clean verify -DskipTests
+# or
+./gradlew clean assemble -x test
+```
+
+If build fails, stop and fix.
+
+## Phase 2: Static Analysis
+
+Maven (common plugins):
+```bash
+mvn -T 4 spotbugs:check pmd:check checkstyle:check
+```
+
+Gradle (if configured):
+```bash
+./gradlew checkstyleMain pmdMain spotbugsMain
+```
+
+## Phase 3: Tests + Coverage
+
+```bash
+mvn -T 4 test
+mvn jacoco:report   # verify 80%+ coverage
+# or
+./gradlew test jacocoTestReport
+```
+
+Report:
+- Total tests, passed/failed
+- Coverage % (lines/branches)
+
+## Phase 4: Security Scan
+
+```bash
+# Dependency CVEs
+mvn org.owasp:dependency-check-maven:check
+# or
+./gradlew dependencyCheckAnalyze
+
+# Secrets (git)
+git secrets --scan  # if configured
+```
+
+## Phase 5: Lint/Format (optional gate)
+
+```bash
+mvn spotless:apply   # if using Spotless plugin
+./gradlew spotlessApply
+```
+
+## Phase 6: Diff Review
+
+```bash
+git diff --stat
+git diff
+```
+
+Checklist:
+- No debugging logs left (`System.out`, `log.debug` without guards)
+- Meaningful errors and HTTP statuses
+- Transactions and validation present where needed
+- Config changes documented
+
+## Output Template
+
+```
+VERIFICATION REPORT
+===================
+Build:     [PASS/FAIL]
+Static:    [PASS/FAIL] (spotbugs/pmd/checkstyle)
+Tests:     [PASS/FAIL] (X/Y passed, Z% coverage)
+Security:  [PASS/FAIL] (CVE findings: N)
+Diff:      [X files changed]
+
+Overall:   [READY / NOT READY]
+
+Issues to Fix:
+1. ...
+2. ...
+```
+
+## Continuous Mode
+
+- Re-run phases on significant changes or every 30–60 minutes in long sessions
+- Keep a short loop: `mvn -T 4 test` + spotbugs for quick feedback
+
+**Remember**: Fast feedback beats late surprises. Keep the gate strict—treat warnings as defects in production systems.