Add restore prefix remapping for fresh-system restores

[olxgdm]

Summary

Closes #73.

This PR adds restore-only prefix remapping so backups registered under an old absolute path can be restored into an equivalent location on a new machine, user account, or home directory layout.

New supported forms:

cfgsync restore --all --from-prefix <old-prefix> --to-prefix <new-prefix>
cfgsync restore <tracked-file> --from-prefix <old-prefix> --to-prefix <new-prefix>

What Changed

• Added --from-prefix and --to-prefix options to cfgsync restore.
• Requires the two remap flags to be provided together.
• Normalizes remap prefixes through the existing path utilities, including ~ expansion.
• Keeps single-file restore lookup based on the tracked original path from the registry.
• Computes remapped destinations only at restore time by replacing the tracked entry's old prefix with the new prefix.
• Preserves existing restore behavior when remap flags are absent.
• Leaves registry.json, stored backup paths, and registry version unchanged.
• Adds an explicit-destination restore overload in StorageManager while preserving the existing original-destination restore API.
• Documents the fresh-system remap workflow in the README.
• Includes IDE project metadata updates already present on the branch.

Behavior Notes

• Prefix matching is path-component aware, so /old/user matches /old/user/.gitconfig but does not match /old/user2/.gitconfig.
• Entries outside --from-prefix fail clearly.
• For restore --all, outside-prefix and per-file restore failures are reported per entry, remaining entries continue restoring, and the command exits non-zero after the batch finishes.
• For single-file restore, an outside-prefix tracked entry fails immediately with a clear error.

Tests Added

• Command-level restore prefix remapping for single-file and --all flows.
• Outside-prefix failure behavior for single-file and batch restore.
• Registry immutability after remapped restore.
• CLI coverage for remapped single-file restore, remapped batch restore, and one-sided remap flag validation.
• StorageManager coverage for explicit destination restore with parent directory creation.

Verification

Ran locally:

cmake -S . -B build -DCFGSYNC_BUILD_TESTS=ON
cmake --build build
ctest --test-dir build --output-on-failure

Result:

100% tests passed, 0 tests failed out of 241

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
92.9% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud