Release secrets-mcp 0.3.0: folder/type schema and MCP folder disambiguation

- Rename namespace/kind to folder/type on entries, audit_log, and history tables;
  add notes. Unique key is (user_id, folder, name).
- Service layer and MCP tools support name-first lookup with optional folder when
  multiple entries share the same name.
- secrets_delete dry_run uses the same disambiguation as real deletes.
- Add scripts/migrate-v0.3.0.sql for manual DB migration. Refresh README and
  AGENTS.md.

Made-with: Cursor

crates/secrets-core/src/service/export.rs

@@ -9,8 +9,8 @@ use crate::models::{ExportData, ExportEntry, ExportFormat};
 use crate::service::search::{fetch_entries, fetch_secrets_for_entries};
 
 pub struct ExportParams<'a> {
-    pub namespace: Option<&'a str>,
-    pub kind: Option<&'a str>,
+    pub folder: Option<&'a str>,
+    pub entry_type: Option<&'a str>,
     pub name: Option<&'a str>,
     pub tags: &'a [String],
     pub query: Option<&'a str>,
@@ -25,8 +25,8 @@ pub async fn export(
 ) -> Result<ExportData> {
     let entries = fetch_entries(
         pool,
-        params.namespace,
-        params.kind,
+        params.folder,
+        params.entry_type,
         params.name,
         params.tags,
         params.query,
@@ -62,9 +62,10 @@ pub async fn export(
         };
 
         export_entries.push(ExportEntry {
-            namespace: entry.namespace.clone(),
-            kind: entry.kind.clone(),
             name: entry.name.clone(),
+            folder: entry.folder.clone(),
+            entry_type: entry.entry_type.clone(),
+            notes: entry.notes.clone(),
             tags: entry.tags.clone(),
             metadata: entry.metadata.clone(),
             secrets,