Add Alerts webapp UI (ticket 020)

New Alerts panel: lists rules with condition summaries and an enabled
toggle, and a condition-type-specific editor (Immediate/Threshold/NewValue/
Ratio) with client-side validation before save, reusing FilterBar's query
input styling for query-based conditions. Adds a test-notification endpoint
(POST /api/settings/alerts/test) so an ntfy topic/server can be verified
without saving a rule first, plus a docs section and help icons matching
ticket 021's pattern.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01XFUNZwCvz3kcod3352ZR2o

src/api.rs

@@ -6,13 +6,13 @@ use crate::dto::{
     BucketValuesParams, CreateAlertRuleRequest, CreateDashboardRequest, CreateProfileRequest,
     CssEntryDto, DashboardDto, ErrorDto, ImportCssRequest, LinkCssRequest, MetricDeclarationDto,
     ParamDeclarationDto, LogsParams, ProfileSummaryDto, PromqlParams, SaveDashboardRequest,
-    SettingsDto, TimelineParams, UpdateAlertRuleRequest, UpdateSettingsRequest,
+    SettingsDto, TestAlertNotificationRequest, TimelineParams, UpdateAlertRuleRequest, UpdateSettingsRequest,
 };
 use crate::engine::{
     DeclareMetricRequest, DeclareParamRequest, EngineHandle, EngineMessage, EngineQuery,
     EngineResponse,
 };
-use crate::alerts::AlertError;
+use crate::alerts::{deliver_ntfy, AlertError};
 use crate::profile::{self, Profile, ProfileError, ProfileStore};
 use crate::settings::{CssError, SettingsHandle};
 use axum::extract::{Path as AxumPath, Query, State};
@@ -110,6 +110,7 @@ pub fn router(engine: EngineHandle, settings: SettingsHandle, settings_path: Pat
             "/api/settings/alerts/{id}",
             put(update_alert_rule).delete(delete_alert_rule),
         )
+        .route("/api/settings/alerts/test", post(test_alert_notification))
         .route("/api/settings/profiles", get(list_profiles).post(create_profile))
         .route("/api/settings/profiles/{name}", delete(delete_profile))
         .route("/api/settings/profiles/{name}/activate", post(activate_profile))
@@ -523,6 +524,19 @@ async fn delete_alert_rule(State(state): State<ApiState>, AxumPath(id): AxumPath
     }
 }
 
+/// `POST /api/settings/alerts/test` — delivers a test notification to an
+/// ntfy topic/server without requiring a saved rule, so the sink can be
+/// verified before saving. Body: `{ "topic": "...", "server": "..." | null }`.
+/// Returns `204 No Content` on success, `502 Bad Gateway` if ntfy rejects
+/// or is unreachable.
+async fn test_alert_notification(Json(body): Json<TestAlertNotificationRequest>) -> impl IntoResponse {
+    let server = body.server.unwrap_or_else(|| "https://ntfy.sh".to_string());
+    match deliver_ntfy(&server, &body.topic, "Test notification from ottyl").await {
+        Ok(()) => StatusCode::NO_CONTENT.into_response(),
+        Err(err) => (StatusCode::BAD_GATEWAY, err).into_response(),
+    }
+}
+
 /// `GET /api/settings` — returns the subset of `Settings` the NavMenu UI
 /// needs (colour scheme, active profile name) as `SettingsDto`. CSS entries
 /// have their own dedicated list endpoint (`GET /api/settings/css`).

src/dto.rs

@@ -259,6 +259,16 @@ pub struct UpdateAlertRuleRequest {
     pub sink: AlertSink,
 }
 
+/// Request body for `POST /api/settings/alerts/test` (ticket 020): delivers
+/// a test notification to an ntfy topic/server without requiring a saved
+/// rule. `server` defaults to `https://ntfy.sh` when absent, same as
+/// `AlertSink::Ntfy`.
+#[derive(Debug, Deserialize)]
+pub struct TestAlertNotificationRequest {
+    pub topic: String,
+    pub server: Option<String>,
+}
+
 /// Summary of one profile for `GET /api/settings/profiles` (ticket 011):
 /// just the name and declaration/dashboard counts the Presets panel needs to
 /// render a list, rather than the full param/metric declaration bodies.