feat: secrets CLI MVP — add/search/delete with PostgreSQL JSONB

- Single `secrets` table with namespace/kind/name/tags/metadata/encrypted
- Auto-migrate on startup using uuidv7() primary keys and GIN indexes
- CLI commands: add (upsert, @file support), search (full-text + tags), delete
- Multi-platform Gitea Actions: debian (x86_64-musl), darwin-arm64, windows
  - continue-on-error + timeout-minutes=30 for offline runner tolerance
- VS Code tasks.json for local build/test/seed
- AGENTS.md for AI context

Made-with: Cursor

src/models.rs

@@ -0,0 +1,17 @@
+use chrono::{DateTime, Utc};
+use serde::{Deserialize, Serialize};
+use serde_json::Value;
+use uuid::Uuid;
+
+#[derive(Debug, Serialize, Deserialize, sqlx::FromRow)]
+pub struct Secret {
+    pub id: Uuid,
+    pub namespace: String,
+    pub kind: String,
+    pub name: String,
+    pub tags: Vec<String>,
+    pub metadata: Value,
+    pub encrypted: Value,
+    pub created_at: DateTime<Utc>,
+    pub updated_at: DateTime<Utc>,
+}