## Compilation Fixes
- Add deprecated compatibility methods to McpService:
* get_servers() - filters servers by app
* set_enabled() - delegates to toggle_app()
* sync_enabled() - syncs enabled servers for specific app
* import_from_claude/codex/gemini() - wraps mcp:: functions
- Fix toml_edit type conversion in sync_single_server_to_codex():
* Add json_server_to_toml_table() helper function
* Manually construct toml_edit::Table instead of invalid serde conversion
- Fix get_codex_config_path() calls (returns PathBuf, not Result)
- Update upsert_mcp_server_in_config() to work with unified structure:
* Converts old per-app API to unified McpServer structure
* Preserves existing server data when updating
* Supports sync_other_side parameter for multi-app enable
- Update delete_mcp_server_in_config() to ignore app parameter
## Backward Compatibility
- All old v3.6.x commands continue to work with deprecation warnings
- Frontend migration can be done incrementally
- Old commands transparently use new unified backend
## Status
✅ Backend compiles successfully (cargo check passes)
⚠️ 16 warnings (8 deprecation + 8 unused functions - expected)
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