feat: add versioned Spring Boot FSM example

[NGirchev]

Summary

• Add an isolated Spring Boot/PostgreSQL example with editable drafts, validated publishing, immutable published versions and orders pinned to their flow version.
• Reuse the core FsmDto JSON and toExTransitionTable() converter; two small factories resolve ordinary Action/Guard Spring beans by name. No separate compiler, transition schema or dynamic behavior interfaces.
• Bound compiled-table caching and require a positive runtime limit whenever synchronous auto transitions are enabled, instead of example-specific cycle analysis.
• Read existing stored JSON through a read-only compatibility adapter; no migration rewrites existing flow versions.
• Fix independent review findings: reject state IDs exceeding the database's 120-character limit and amounts that cannot be stored exactly as NUMERIC(19,2).
• Preserve valid trailing-zero amounts and report invalid amounts as HTTP 400 before database access.
• Update vulnerable dependencies, including Vitest 4.1.11.

Verification

• Independent subagent review against master.
• Regression tests reproduced the state-length, amount and HTTP handling failures before the fixes; focused tests passed after them.
• Core quality/tests/coverage and all non-Docker example tests passed.
• Editor: npm test -- --run (59 tests), npm run build, npm audit --audit-level=moderate (0 vulnerabilities).
• Simplification regression tests cover core JSON round trips, real Spring bean injection, post-actions, unknown behavior IDs, database bounds, runtime limits and legacy JSON reading. Local core checks and all non-Docker example tests passed.
• Docker is not running locally; GitHub CI passed on the simplified implementation, including PostgreSQL integration, build, Detekt and coverage gates: https://github.com/NGirchev/fsm/actions/runs/35385046601.

Branch relationship

Related: #6 (WIP modularization/transactional example), a separate branch from the same master commit, not an ancestor or replacement. Core layout/runtime and dependency changes overlap; reconcile the second PR after the first is merged.