feat: add ln=target link colours and configurable filename quoting

[fxrdhan]

Description

This PR ports two user-facing features from eza-community/eza into lsr, one atomic commit per item:

1. Commit eae525eb: feat(theme): support ln=target in LS_COLORS (ported from eza-community/eza#1018, itself a port of Support ln=target in LS_COLORS (#774) ogham/exa#960)

   • ln=target colours a symbolic link the same way as the file it points at instead of using a fixed link style; orphaned links keep the broken-symlink colour.
   • The link kind style becomes a LinkStyle that is either an explicit ANSI style or the target-following mode, accepted from both LS_COLORS/EZA_COLORS and theme.yml (filekinds.symlink now understands the literal target).
   • Hardening over upstream: target resolution reuses a shared per-file style helper instead of reconstructing a temporary FileName, so chained or missing targets can never panic — broken targets fall back to or=, absent ones stay unstyled.

2. Commit 559a7deb: feat(options): add --quotes flag and quoting-style environment variable (ported from eza-community/eza#587)

   • Replaces the boolean --no-quotes switch with --quotes=(always|auto|never), mirroring GNU ls quoting styles: auto wraps only names with spaces or quotes, always quotes every name, never quotes nothing.
   • New LSR_QUOTING_STYLE / EZA_QUOTING_STYLE environment variable supplies the default; the command line overrides it, invalid values fall back to auto. The old flag stays as a hidden compatibility alias.
   • Adapted to lsr's clap architecture (upstream's diff predates it) and routed through the mockable Vars trait rather than raw std::env for testability.
   • Updates all five shell completions, both man pages (--quotes + env var section), and the README.

Quality Gates

• cargo fmt --all -- --check
• cargo clippy --all-targets --all-features — 0 warnings
• cargo test --workspace — all green (new: ls_ln_target, borrow/orphan paint tests, 6 quote deduce tests)
• reuse lint — 100% compliant
• Conventional Commits