feat(core): add backup deps + error variants

Adds zstd, tar, base64 to relicario-core; introduces
BackupBadMagic / BackupUnsupportedVersion / BackupSchemaMismatch.
Foundation for the backup module landing in Task 2.

Cargo.lock

@@ -275,6 +275,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "43c5703da9466b66a946814e1adf53ea2c90f10063b86290cc9eb67ce3478a20"
 dependencies = [
  "find-msvc-tools",
+ "jobserver",
+ "libc",
  "shlex",
 ]
 
@@ -651,6 +653,17 @@ version = "0.2.9"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "28dea519a9695b9977216879a3ebfddf92f1c08c05d984f8996aecd6ecdc811d"
 
+[[package]]
+name = "filetime"
+version = "0.2.27"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f98844151eee8917efc50bd9e8318cb963ae8b297431495d3f758616ea5c57db"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "libredox",
+]
+
 [[package]]
 name = "find-msvc-tools"
 version = "0.1.9"
@@ -748,6 +761,18 @@ dependencies = [
  "wasm-bindgen",
 ]
 
+[[package]]
+name = "getrandom"
+version = "0.3.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "899def5c37c4fd7b2664648c28120ecec138e4d395b459e5ca34f9cce2dd77fd"
+dependencies = [
+ "cfg-if",
+ "libc",
+ "r-efi 5.3.0",
+ "wasip2",
+]
+
 [[package]]
 name = "getrandom"
 version = "0.4.2"
@@ -756,7 +781,7 @@ checksum = "0de51e6874e94e7bf76d726fc5d13ba782deca734ff60d5bb2fb2607c7406555"
 dependencies = [
  "cfg-if",
  "libc",
- "r-efi",
+ "r-efi 6.0.0",
  "wasip2",
  "wasip3",
 ]
@@ -1008,6 +1033,16 @@ version = "1.0.18"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8f42a60cbdf9a97f5d2305f08a87dc4e09308d1276d28c869c684d7777685682"
 
+[[package]]
+name = "jobserver"
+version = "0.1.34"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9afb3de4395d6b3e67a780b6de64b51c978ecf11cb9a462c66be7d4ca9039d33"
+dependencies = [
+ "getrandom 0.3.4",
+ "libc",
+]
+
 [[package]]
 name = "js-sys"
 version = "0.3.95"
@@ -1050,7 +1085,10 @@ version = "0.1.16"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e02f3bb43d335493c96bf3fd3a321600bf6bd07ed34bc64118e9293bdffea46c"
 dependencies = [
+ "bitflags",
  "libc",
+ "plain",
+ "redox_syscall 0.7.4",
 ]
 
 [[package]]
@@ -1268,7 +1306,7 @@ checksum = "2621685985a2ebf1c516881c026032ac7deafcda1a2c9b7850dc81e3dfcb64c1"
 dependencies = [
  "cfg-if",
  "libc",
- "redox_syscall",
+ "redox_syscall 0.5.18",
  "smallvec",
  "windows-link",
 ]
@@ -1306,6 +1344,18 @@ dependencies = [
  "spki",
 ]
 
+[[package]]
+name = "pkg-config"
+version = "0.3.33"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "19f132c84eca552bf34cab8ec81f1c1dcc229b811638f9d283dceabe58c5569e"
+
+[[package]]
+name = "plain"
+version = "0.2.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "b4596b6d070b27117e987119b4dac604f3c58cfb0b191112e24771b2faeac1a6"
+
 [[package]]
 name = "png"
 version = "0.18.1"
@@ -1424,6 +1474,12 @@ dependencies = [
  "proc-macro2",
 ]
 
+[[package]]
+name = "r-efi"
+version = "5.3.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "69cdb34c158ceb288df11e18b4bd39de994f6657d83847bdffdbd7f346754b0f"
+
 [[package]]
 name = "r-efi"
 version = "6.0.0"
@@ -1469,6 +1525,15 @@ dependencies = [
  "bitflags",
 ]
 
+[[package]]
+name = "redox_syscall"
+version = "0.7.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f450ad9c3b1da563fb6948a8e0fb0fb9269711c9c73d9ea1de5058c79c8d643a"
+dependencies = [
+ "bitflags",
+]
+
 [[package]]
 name = "redox_users"
 version = "0.4.6"
@@ -1539,6 +1604,7 @@ name = "relicario-core"
 version = "0.2.0"
 dependencies = [
  "argon2",
+ "base64",
  "bip39",
  "chacha20poly1305",
  "chrono",
@@ -1552,10 +1618,12 @@ dependencies = [
  "serde_json",
  "sha1",
  "sha2",
+ "tar",
  "thiserror 2.0.18",
  "unicode-normalization",
  "url",
  "zeroize",
+ "zstd",
  "zxcvbn",
 ]
 
@@ -1807,6 +1875,16 @@ dependencies = [
  "syn",
 ]
 
+[[package]]
+name = "tar"
+version = "0.4.45"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "22692a6476a21fa75fdfc11d452fda482af402c008cdbaf3476414e122040973"
+dependencies = [
+ "filetime",
+ "libc",
+]
+
 [[package]]
 name = "tempfile"
 version = "3.27.0"
@@ -2710,6 +2788,34 @@ version = "1.0.21"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "b8848ee67ecc8aedbaf3e4122217aff892639231befc6a1b58d29fff4c2cabaa"
 
+[[package]]
+name = "zstd"
+version = "0.13.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e91ee311a569c327171651566e07972200e76fcfe2242a4fa446149a3881c08a"
+dependencies = [
+ "zstd-safe",
+]
+
+[[package]]
+name = "zstd-safe"
+version = "7.2.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "8f49c4d5f0abb602a93fb8736af2a4f4dd9512e36f7f570d66e65ff867ed3b9d"
+dependencies = [
+ "zstd-sys",
+]
+
+[[package]]
+name = "zstd-sys"
+version = "2.0.16+zstd.1.5.7"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "91e19ebc2adc8f83e43039e79776e3fda8ca919132d68a1fed6a5faca2683748"
+dependencies = [
+ "cc",
+ "pkg-config",
+]
+
 [[package]]
 name = "zune-core"
 version = "0.5.1"

crates/relicario-core/Cargo.toml

@@ -26,5 +26,8 @@ chrono = { version = "0.4", default-features = false, features = ["serde", "cloc
 hex = "0.4"
 url = { version = "2", features = ["serde"] }
 getrandom = "0.2"
+zstd = { version = "0.13", default-features = false }
+tar = { version = "0.4", default-features = false }
+base64 = "0.22"
 
 [dev-dependencies]

crates/relicario-core/src/error.rs

@@ -39,6 +39,18 @@ pub enum RelicarioError {
     #[error("unsupported vault format version: found 0x{found:02x}, expected 0x{expected:02x}")]
     UnsupportedFormatVersion { found: u8, expected: u8 },
 
+    /// Backup file's first 4 bytes don't match the "RBAK" magic.
+    #[error("not a relicario backup file")]
+    BackupBadMagic,
+
+    /// Backup format version is newer than this binary supports.
+    #[error("backup created by a newer relicario; upgrade required")]
+    BackupUnsupportedVersion { found: u8, expected: u8 },
+
+    /// Backup envelope schema version doesn't match.
+    #[error("backup envelope schema v{found}; this relicario reads v{expected}")]
+    BackupSchemaMismatch { found: u32, expected: u32 },
+
     /// An item was looked up by ID but does not exist in the manifest.
     #[error("item not found: {0}")]
     ItemNotFound(String),
@@ -130,4 +142,18 @@ mod tests {
         assert!(s.contains("01") || s.contains("1"));
         assert!(s.contains("02") || s.contains("2"));
     }
+
+    #[test]
+    fn backup_errors_carry_useful_messages() {
+        let bad = RelicarioError::BackupBadMagic;
+        assert!(format!("{}", bad).contains("not a relicario backup file"));
+
+        let ver = RelicarioError::BackupUnsupportedVersion { found: 0x02, expected: 0x01 };
+        let s = format!("{}", ver);
+        assert!(s.contains("newer"));
+
+        let schema = RelicarioError::BackupSchemaMismatch { found: 2, expected: 1 };
+        let s = format!("{}", schema);
+        assert!(s.contains("v2") && s.contains("v1"));
+    }
 }