feat: initial import — SVN↔Git bi-directional mirror for Gitea

Server-side sidecar daemon. Uses own SQLite mapping table (not git svn)
so Git commit hashes never change. Pure Python, zero framework deps.

Includes:
- SVN→Git sync engine with nested-directory tree reconstruction
- Git→SVN push with author mapping and working-copy management
- Branch/tag sync (svn copy → git branch/tag and reverse)
- Gitea integration (on-disk push/fetch, webhook receiver)
- Reconciliation tool for divergence recovery (assess + auto-fix)
- Full end-to-end regression test (bash, 34 checks)
- systemd unit and deployment docs

Only external dependency: PyYAML (config parsing).

.gitignore

@@ -0,0 +1,24 @@
+# Python
+__pycache__/
+*.py[cod]
+*.egg-info/
+dist/
+build/
+
+# Editor / OS
+.DS_Store
+*.swp
+*.swo
+*~
+
+# IDE
+.idea/
+.vscode/
+*.iml
+
+# Mirror runtime data (generated by the tool)
+/var/svn-mirror/
+
+# Temp files
+/tmp/
+*.tmp