Implement live configuration reload

[duaraghav8]

Motivation

• Ensure the config-sync feature uses an absolute, well-formed default directory instead of returning a raw ~/.mcpjungle string so downstream code and consumers get a concrete path.
• Wire up the config-sync feature end-to-end so the server can optionally manage desired-state entities from a directory, track them, and keep them live-synced.
• Provide safe guardrails for adoption of manual entities, admin user protection, and preserving last-good state on parse/validation errors.

Description

• Add DefaultConfigSyncDirName constant and change getConfigSyncDir() to resolve the current user home via os.UserHomeDir() and return filepath.Join(home, DefaultConfigSyncDirName) with a fallback to filepath.Join("~", DefaultConfigSyncDirName) when home resolution fails.
• Add CLI flags --config-sync and --config-dir and env var support (MCPJUNGLE_CONFIG_SYNC_ENABLED, MCPJUNGLE_CONFIG_DIR), and wire a new configsync service into startup so it is initialized and started when enabled.
• Introduce a ManagedConfigFile model and include it in migrations, and implement a full configsync service that resolves the config dir, ensures subdirectories, watches with fsnotify, and reconciles mcp_servers, mcp_clients, groups, and users with adoption, tracking, and error aggregation behavior.
• Update README.md to document the auto-synced config directory feature, layout, behavior, and guardrails, and add/update unit tests for CLI helpers and config-sync behaviors.

Testing

• Ran the focused cmd unit test go test -vet=off ./cmd -run '^TestGetConfigSyncDir$' -count=1, which passed.
• Ran gofmt on modified files and committed the changes.

---

Codex Task

[duaraghav8]

addresses #142