Initial commit: APT-DNF Bridge workspace

- Core crate: Minimal shell-out implementation
- Advanced crate: Pluggable backends and enhanced features
- Main crate: Re-exports core + optional advanced features
- Feature flags: Users choose complexity level
- Examples: Working demonstrations of both approaches
- Documentation: Clear README explaining the structure

Implements the refined two-crate approach with workspace + feature flags.

apt-dnf-bridge/Cargo.toml

@@ -0,0 +1,37 @@
+[package]
+name = "apt-dnf-bridge"
+version.workspace = true
+edition.workspace = true
+description = "DNF-like API for APT, with optional advanced features"
+license.workspace = true
+repository.workspace = true
+keywords.workspace = true
+categories.workspace = true
+
+[dependencies]
+apt-dnf-bridge-core = { path = "../apt-dnf-bridge-core" }
+apt-dnf-bridge-advanced = { path = "../apt-dnf-bridge-advanced", optional = true }
+tokio = { workspace = true, features = ["macros", "rt-multi-thread"] }
+
+[features]
+default = []  # Core-only by default
+advanced = ["apt-dnf-bridge-advanced"]
+
+[dev-dependencies]
+tempfile.workspace = true
+
+[[example]]
+name = "basic_usage"
+path = "../examples/basic_usage.rs"
+
+[[example]]
+name = "package_query"
+path = "../examples/package_query.rs"
+
+[[example]]
+name = "atomicity_notes"
+path = "../examples/atomicity_notes.rs"
+
+[[example]]
+name = "backend_selection"
+path = "../examples/backend_selection.rs"