feat: file dedup — content_hash SHA256 + /files/lookup API + auto-rename on name collision

src/core/storage/content_hash.rs

@@ -0,0 +1,18 @@
+use sha2::{Digest, Sha256};
+use std::io::Read;
+use std::path::Path;
+use anyhow::Result;
+
+/// Compute SHA256 of the entire file content
+pub fn compute_sha256(path: &Path) -> Result<String> {
+    let mut file = std::fs::File::open(path)?;
+    let mut hasher = Sha256::new();
+    let mut buf = [0u8; 65536];
+    loop {
+        let n = file.read(&mut buf)?;
+        if n == 0 { break; }
+        hasher.update(&buf[..n]);
+    }
+    let hash = format!("{:x}", hasher.finalize());
+    Ok(hash)
+}

src/core/storage/mod.rs

@@ -1,7 +1,9 @@
+pub mod content_hash;
 pub mod file_manager;
 pub mod output_dir;
 pub mod uuid;
 
+pub use content_hash::compute_sha256;
 pub use file_manager::FileManager;
 pub use output_dir::OutputDir;
 pub use uuid::compute_uuid;