feat(plugins): plugin pages, per-user config, capabilities gate, mobile/telegram refactors

- Plugin HTTP routes + web pages (plugin-page-host, plugin-catalog, plugin-detail)
- Plugin access grants + per-user config (DB tables + API + frontend forms)
- Capabilities-based guard (caps.rs) replacing role-id checks
- Mobile connector: message routing, payload types, router refactor
- Telegram bot: auth flow, event handling improvements
- Honcho plugin: substantial rework
- Sidebar: plugin pages integration, role-driven visibility
- i18n: new strings for plugins, connectors, capabilities
- Remove unused mascot asset

crates/skald-core/src/skald/accessors.rs

@@ -177,4 +177,16 @@ impl UserChannelApi for Skald {
         let ctx = self.user_context(user_id).await?;
         Some(std::sync::Arc::new(UserContextHandle::new(ctx)))
     }
+
+    async fn plugin_access(&self, plugin_id: &str, user_id: &str) -> bool {
+        // Admin short-circuit + grant lookup live in `db::plugin_access`; a
+        // lookup error fails closed.
+        crate::db::plugin_access::effective_access(self.db(), plugin_id, user_id)
+            .await
+            .unwrap_or(false)
+    }
+
+    async fn user_for_session(&self, token: &str) -> Option<String> {
+        self.sessions().user_of(token)
+    }
 }