fix: add --meta filtering support to client/server list mode

Plumb metadata filter from client CLI through the HTTP API to the
server's data_service.list_items(). The server accepts a JSON-encoded
meta query parameter where null values mean 'key exists' and string
values mean 'exact match'.

Also fix LZ4 compression round-trip for client mode:
- Explicit flush FrameEncoder before drop to avoid sending only the
  frame header when compress=false
- Send _client_compression metadata so client knows actual compression
  on retrieval (server records compression=None when compress=false)
- Use FrameDecoder (frame format) instead of decompress_size_prepended
  (size-prepended format) to match server storage format

src/modes/client/get.rs

@@ -23,14 +23,14 @@ pub fn mode(
         ids[0]
     } else if !tags.is_empty() {
         // Find item by tags
-        let items = client.list_items(tags, "newest", 0, 1)?;
+        let items = client.list_items(tags, "newest", 0, 1, &std::collections::HashMap::new())?;
         if items.is_empty() {
             return Err(anyhow::anyhow!("No items found matching tags: {:?}", tags));
         }
         items[0].id
     } else {
         // Get latest item
-        let items = client.list_items(&[], "newest", 0, 1)?;
+        let items = client.list_items(&[], "newest", 0, 1, &std::collections::HashMap::new())?;
         if items.is_empty() {
             return Err(anyhow::anyhow!("No items found"));
         }
@@ -60,8 +60,17 @@ pub fn mode(
         }
     }
 
-    // Decompress locally
-    let compression_type = CompressionType::from_str(&compression).unwrap_or(CompressionType::None);
+    // Decompress locally.
+    // Prefer _client_compression metadata (set by client save) over the server-reported
+    // compression header, because when compress=false the server stores compressed bytes
+    // but records compression=None.
+    let effective_compression = item_info
+        .metadata
+        .get("_client_compression")
+        .map(|s| s.as_str())
+        .unwrap_or(&compression);
+    let compression_type =
+        CompressionType::from_str(effective_compression).unwrap_or(CompressionType::None);
 
     let decompressed = match compression_type {
         CompressionType::GZip => {
@@ -71,8 +80,13 @@ pub fn mode(
             decoder.read_to_end(&mut content)?;
             content
         }
-        CompressionType::LZ4 => lz4_flex::decompress_size_prepended(&raw_bytes)
-            .map_err(|e| anyhow::anyhow!("LZ4 decompression failed: {}", e))?,
+        CompressionType::LZ4 => {
+            use lz4_flex::frame::FrameDecoder;
+            let mut decoder = FrameDecoder::new(&raw_bytes[..]);
+            let mut content = Vec::new();
+            decoder.read_to_end(&mut content)?;
+            content
+        }
         _ => raw_bytes,
     };