fix: correct critical bugs and improve pipe streaming performance

Critical bug fixes:
- save_item now returns real Item from database, not a hardcoded fake
- AsyncDataService::save() reuses self.sync_service instead of creating redundant instance
- GenerateStatus trait signature mismatch fixed (CLI/API decoupling)

Performance improvements (pipe path untouched):
- CompressionEngine::open() returns Box<dyn Read + Send> enabling true streaming
- mode_get eliminates triple full-file read (was sampling then re-reading entire file)
- FilteringReader adds fast-path bypass when no filters, pre-allocates temp buffer
- text.rs meta plugin processes &[u8] slice directly, eliminates data.to_vec() clone

API correctness:
- Tag parse errors now return 400 instead of being silently discarded
- compute_diff uses similar crate (LCS-based) instead of naive positional comparison

Cleanup:
- Modernize string formatting (format!({x})) across codebase
- Remove redundant DB query in get mode
- Derive Debug/ToSchema on public types
- Delete placeholder test files with no real assertions
- Extract parse_comma_tags utility function

src/config.rs

@@ -189,10 +189,7 @@ pub struct Settings {
 impl Settings {
     /// Create unified settings from config and args with proper priority
     pub fn new(args: &Args, default_dir: PathBuf) -> Result<Self> {
-        debug!(
-            "CONFIG: Creating settings with default dir: {:?}",
-            default_dir
-        );
+        debug!("CONFIG: Creating settings with default dir: {default_dir:?}");
 
         let config_path = if let Some(config_path) = &args.options.config {
             config_path.clone()
@@ -208,21 +205,21 @@ impl Settings {
             } else {
                 PathBuf::from("~/.config/keep/config.yml")
             };
-            debug!("CONFIG: Using default config path: {:?}", default_path);
+            debug!("CONFIG: Using default config path: {default_path:?}");
             default_path
         };
 
-        debug!("CONFIG: Using config path: {:?}", config_path);
+        debug!("CONFIG: Using config path: {config_path:?}");
 
         let mut config_builder = config::Config::builder();
 
         // Load config file if it exists
         if config_path.exists() {
-            debug!("CONFIG: Loading config file: {:?}", config_path);
+            debug!("CONFIG: Loading config file: {config_path:?}");
             config_builder =
                 config_builder.add_source(config::File::from(config_path.clone()).required(false));
         } else {
-            debug!("CONFIG: Config file does not exist: {:?}", config_path);
+            debug!("CONFIG: Config file does not exist: {config_path:?}");
         }
 
         // Add environment variables
@@ -234,7 +231,7 @@ impl Settings {
 
         // Override with CLI args
         if let Some(dir) = &args.options.dir {
-            debug!("CONFIG: Overriding dir with CLI arg: {:?}", dir);
+            debug!("CONFIG: Overriding dir with CLI arg: {dir:?}");
             config_builder = config_builder.set_override("dir", dir.to_str().unwrap())?;
         }
 
@@ -302,7 +299,7 @@ impl Settings {
 
         match config.try_deserialize::<Settings>() {
             Ok(mut settings) => {
-                debug!("CONFIG: Successfully deserialized settings: {:?}", settings);
+                debug!("CONFIG: Successfully deserialized settings: {settings:?}");
 
                 // Set defaults for list_format if not provided
                 if settings.list_format.is_empty() {
@@ -393,15 +390,15 @@ impl Settings {
 
                 // Set dir to default if not provided or is empty
                 if settings.dir == PathBuf::new() {
-                    debug!("CONFIG: Setting default dir: {:?}", default_dir);
+                    debug!("CONFIG: Setting default dir: {default_dir:?}");
                     settings.dir = default_dir;
                 }
 
-                debug!("CONFIG: Final settings: {:?}", settings);
+                debug!("CONFIG: Final settings: {settings:?}");
                 Ok(settings)
             }
             Err(e) => {
-                error!("CONFIG: Failed to deserialize settings: {}", e);
+                error!("CONFIG: Failed to deserialize settings: {e}");
                 Err(e.into())
             }
         }
@@ -422,9 +419,9 @@ impl Settings {
         if let Some(server) = &self.server {
             // First check for password_file
             if let Some(password_file) = &server.password_file {
-                debug!("CONFIG: Reading password from file: {:?}", password_file);
+                debug!("CONFIG: Reading password from file: {password_file:?}");
                 let password = fs::read_to_string(password_file)
-                    .with_context(|| format!("Failed to read password file: {:?}", password_file))?
+                    .with_context(|| format!("Failed to read password file: {password_file:?}"))?
                     .trim()
                     .to_string();
                 return Ok(Some(password));