feat: entry update links existing secrets (link_secret_names)

- secrets-core: update flow validates and applies secret links
- secrets-mcp: MCP tool params and UI for managing links on edit
- Align errors and templates; minor crypto/.gitignore tweaks

Made-with: Cursor

crates/secrets-mcp/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "secrets-mcp"
-version = "0.4.0"
+version = "0.5.0"
 edition.workspace = true
 
 [[bin]]