Add custom dictionary corrections

[jguice]

Summary

• add a local custom dictionary file and cross-platform CLI management commands
• apply dictionary replacements after transcription cleanup and hot-reload dictionary edits on the next dictation
• add macOS clipboard restore-after-paste config/menu support so dictated text does not remain in the clipboard by default

Verification

• cargo test
• cargo build
• cargo build --release && ./scripts/make-bundle.sh
• cross-compile check to x86_64-unknown-linux-gnu via the pinned 1.95 toolchain
• CLI smoke: bare dictionary add rejects missing --replace; add/list works with a temp HOME
• clippy clean: cargo clippy --locked --all-targets -- -D warnings