feat: add comprehensive CLI with API client, session management, and data seeding

- Binary renamed from 'api' to 'xevion' with full CLI command structure
- Authentication: login/logout with session persistence to .xevion-session
- API commands: projects, tags, settings CRUD operations with JSON/table output
- Serve command: run production server with configurable listen addresses
- Seed command: moved from bin/ to CLI subcommand for database initialization
- HTTP client abstraction supporting both TCP and Unix socket connections

src/db/settings.rs

@@ -60,7 +60,7 @@ pub struct ApiSiteSettings {
 }
 
 // Request types for updates
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, Serialize)]
 pub struct UpdateSiteIdentityRequest {
     #[serde(rename = "displayName")]
     pub display_name: String,
@@ -70,7 +70,7 @@ pub struct UpdateSiteIdentityRequest {
     pub site_title: String,
 }
 
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, Serialize)]
 pub struct UpdateSocialLinkRequest {
     pub id: String,
     pub platform: String,
@@ -82,7 +82,7 @@ pub struct UpdateSocialLinkRequest {
     pub display_order: i32,
 }
 
-#[derive(Debug, Deserialize)]
+#[derive(Debug, Deserialize, Serialize)]
 pub struct UpdateSiteSettingsRequest {
     pub identity: UpdateSiteIdentityRequest,
     #[serde(rename = "socialLinks")]