feat(EM-32): Extract and version ftgo-common shared library

[devin-ai-integration]

feat(EM-32): Extract and version ftgo-common shared library

Summary

Extracts the monolith's ftgo-common module into libs/ftgo-common/ as a standalone, versioned shared library targeting Java 17 / Spring Boot 3.2 / Jakarta namespace.

What changed:

• Copied all 8 source files from ftgo-common/src/ into libs/ftgo-common/src/ under the new com.ftgo.common package
• Migrated javax.persistence → jakarta.persistence and javax.annotation → jakarta.annotation
• Replaced commons-lang EqualsBuilder/HashCodeBuilder/ToStringBuilder in Money.java with java.util.Objects
• Rewrote build.gradle with explicit dependencies (Jakarta Persistence 3.1, Jackson 2.15, Spring Boot 3.2, JUnit 5)
• Added settings.gradle so the library can build independently (gradle build from libs/ftgo-common/)
• Added unit tests for Money, Address, PersonName, UnsupportedStateTransitionException, and MoneyModule serialization
• Added README.md documenting the library API

No monolith source files or root settings.gradle were modified.

Review & Testing Checklist for Human

• Money.equals() uses BigDecimal.equals() which is scale-sensitive (new BigDecimal("10.0") ≠ new BigDecimal("10")). This matches the original behavior but could be a latent bug for consumers—confirm this is acceptable or consider compareTo == 0.
• MoneyModule uses deprecated ctxt.mappingException() (Jackson 2.15 deprecation warning emitted during build). Verify this is acceptable or should be replaced with ctxt.handleUnexpectedToken().
• settings.gradle coexistence: A standalone settings.gradle was added for independent buildability. When this module is eventually wired into the root Gradle build, confirm this won't conflict—may need to be removed or conditioned at that point.
• Address and PersonName lack equals/hashCode: Same as the original monolith, but as JPA embeddables/value objects this is a gap worth considering.
• Recommended test plan: Clone the branch, run cd libs/ftgo-common && gradle build with JDK 17+ to verify compilation and all 19 tests pass. Spot-check that no monolith files under ftgo-common/ were modified.

Notes

• Money.ZERO is not final—carried over from the original source
• Dependency versions are hard-coded in build.gradle; a version catalog can be introduced in a follow-up when the root build is modernized
• Library was verified building independently with Gradle 8.5 + JDK 17 (all tests green)

Link to Devin run: https://app.devin.ai/sessions/55ac098d3ebb428a9632461a5597df0d
Requested by: @abj453demo

[devin-ai-integration]

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