feat(ui): contribution graph with daily activity heatmap

Add /v1/activity/daily endpoint returning per-day event counts via
generate_series + LEFT JOIN. Frontend renders an SVG contribution
graph with circles colored by quantile-based thresholds. Clicking a
day navigates to /activity/YYYY-MM-DD showing that day's events.

New /activity/:timespan route parses single dates (YYYY-MM-DD) and
ranges (YYYY-MM-DD..YYYY-MM-DD) from the URL to initialize the
activity timeline filter.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

crates/moments-api/src/main.rs

@@ -7,11 +7,11 @@ use axum::{
     response::IntoResponse,
     routing::get,
 };
-use chrono::{DateTime, Utc};
+use chrono::{DateTime, NaiveDate, Utc};
 use clap::Parser;
 use moments_core::{EventReader, reshape};
 use moments_data::PgStore;
-use moments_entities::{EventQuery, ProjectSummary, Source, SourceSummary, TimelineItem};
+use moments_entities::{DailyCount, EventQuery, ProjectSummary, Source, SourceSummary, TimelineItem};
 use serde::Deserialize;
 use tower_http::{cors::CorsLayer, trace::TraceLayer};
 use tracing::info;
@@ -56,6 +56,7 @@ async fn main() -> anyhow::Result<()> {
         .route("/v1/events", get(list_events))
         .route("/v1/sources", get(list_sources))
         .route("/v1/projects", get(list_projects))
+        .route("/v1/activity/daily", get(daily_counts))
         .route("/v1/forge/{source}/{*rest}", get(forge_proxy))
         .with_state(state)
         .layer(TraceLayer::new_for_http())
@@ -139,6 +140,22 @@ async fn list_projects(
     Ok(Json(projects))
 }
 
+#[derive(Debug, Deserialize)]
+struct DailyCountsParams {
+    from: Option<NaiveDate>,
+    to: Option<NaiveDate>,
+}
+
+async fn daily_counts(
+    State(state): State<AppState>,
+    Query(params): Query<DailyCountsParams>,
+) -> Result<Json<Vec<DailyCount>>, ApiError> {
+    let to = params.to.unwrap_or_else(|| Utc::now().date_naive());
+    let from = params.from.unwrap_or_else(|| to - chrono::Duration::days(365));
+    let counts = state.store.daily_counts(from, to).await.map_err(internal)?;
+    Ok(Json(counts))
+}
+
 /// Allowlisted forge hosts that the proxy may contact.
 const ALLOWED_HOSTS: &[&str] = &["api.github.com", "git.lair.cafe"];
 

crates/moments-core/src/lib.rs

@@ -5,7 +5,8 @@ pub use presentation::reshape;
 pub use sources::{EventSource, PollerState, PollerStateStore, SourceError, run_poller};
 
 use async_trait::async_trait;
-use moments_entities::{Event, EventQuery, ProjectSummary, SourceSummary};
+use chrono::NaiveDate;
+use moments_entities::{DailyCount, Event, EventQuery, ProjectSummary, SourceSummary};
 
 #[derive(Debug, thiserror::Error)]
 pub enum StoreError {
@@ -19,6 +20,7 @@ pub trait EventReader: Send + Sync {
     async fn list_events(&self, query: &EventQuery) -> Result<Vec<Event>, StoreError>;
     async fn source_summaries(&self, include_private: bool) -> Result<Vec<SourceSummary>, StoreError>;
     async fn list_projects(&self) -> Result<Vec<ProjectSummary>, StoreError>;
+    async fn daily_counts(&self, from: NaiveDate, to: NaiveDate) -> Result<Vec<DailyCount>, StoreError>;
 }
 
 /// Write-side port consumed by `moments-worker`. Idempotent upserts on `id`.

crates/moments-data/src/lib.rs

@@ -8,7 +8,8 @@ pub mod hg;
 use async_trait::async_trait;
 use chrono::{DateTime, Utc};
 use moments_core::{EventReader, EventWriter, PollerState, PollerStateStore, StoreError};
-use moments_entities::{Event, EventQuery, ProjectSummary, Source, SourceSummary};
+use chrono::NaiveDate;
+use moments_entities::{DailyCount, Event, EventQuery, ProjectSummary, Source, SourceSummary};
 use sqlx::Row;
 use sqlx::postgres::{PgPool, PgPoolOptions};
 use std::str::FromStr;
@@ -192,6 +193,35 @@ impl EventReader for PgStore {
             })
             .collect()
     }
+
+    async fn daily_counts(&self, from: NaiveDate, to: NaiveDate) -> Result<Vec<DailyCount>, StoreError> {
+        let rows = sqlx::query(
+            r#"
+            SELECT d::date AS date,
+                   COUNT(e.id)::bigint AS count
+            FROM generate_series($1::date, $2::date, '1 day') d
+            LEFT JOIN events e
+              ON e.occurred_at >= d AND e.occurred_at < d + interval '1 day'
+              AND e.public = true
+            GROUP BY d::date
+            ORDER BY d::date
+            "#,
+        )
+        .bind(from)
+        .bind(to)
+        .fetch_all(&self.pool)
+        .await
+        .map_err(map_err)?;
+
+        rows.into_iter()
+            .map(|r| {
+                Ok(DailyCount {
+                    date: r.try_get("date").map_err(map_err)?,
+                    count: r.try_get("count").map_err(map_err)?,
+                })
+            })
+            .collect()
+    }
 }
 
 #[async_trait]

crates/moments-entities/src/lib.rs

@@ -84,6 +84,13 @@ pub struct SourceSummary {
     pub latest: Option<DateTime<Utc>>,
 }
 
+/// Per-day event count for the contribution graph.
+#[derive(Debug, Clone, Serialize, Deserialize)]
+pub struct DailyCount {
+    pub date: chrono::NaiveDate,
+    pub count: i64,
+}
+
 /// Per-repo activity rollup for the dashboard.
 #[derive(Debug, Clone, Serialize, Deserialize)]
 pub struct ProjectSummary {