feat: support git repositories and project management

- Git (JGit) log fetching: mirror clone cache, incremental fetch, time/author filter, HTTPS token & SSH key auth
- Git preset management and /api/git/* endpoints (test-connection, version-range, fetch)
- Markdown report generalization: project meta, commit range, short hash entries
- Project management: project entities, drag-drop repo assignment, sorting, rename sync, non-empty delete protection
- AI analysis: project-based grouping merges SVN+Git commits, excludes empty projects from Excel
- Batch fetch: skip repos without logs instead of aborting the whole flow
- Frontend: project management page, repo page project dropdown, Git fields, sidebar updates
- Tests: GitLogFetcherTest, DateRangeResolverTest, ProjectConfigServiceTest, merge/exclusion coverage

.gitignore

@@ -1,5 +1,6 @@
 # frontend-vue (Vue 3 + Vite)
 frontend-vue/node_modules/
+frontend-vue/node/
 
 # frontend build output (auto-generated by Docker build)
 src/main/resources/static/v2/