feat: add native zstd compression plugin and deduplicate shared compression/meta utilities

- Add zstd crate (v0.13) with native Rust compression engine (level 3)
- Gate behind 'zstd' feature flag, fall back to program-based when disabled
- Extract CompressionService::decompressing_reader/compressing_writer with zstd support
- Extract MetaService::with_collector() to eliminate Arc<Mutex<Vec>> boilerplate
- Extract read_with_bounds() helper for skip+read pattern
- Add input validation for mutually exclusive --id and --tags flags
- Add zstd round-trip tests

Cargo.lock

@@ -1732,6 +1732,7 @@ dependencies = [
  "uzers",
  "which",
  "xdg",
+ "zstd",
 ]
 
 [[package]]
@@ -4048,3 +4049,31 @@ dependencies = [
  "log",
  "simd-adler32",
 ]
+
+[[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",
+]