Add feature batch 2, subscription/recurring sync, smooth charts, and app icon

- Implement subscriptions view with bidirectional recurring transaction sync
- Add cascade delete/pause/resume between subscriptions and recurring
- Fix foreign key constraints when deleting recurring transactions
- Add cross-view instant refresh via callback pattern
- Replace Bezier chart smoothing with Fritsch-Carlson monotone Hermite interpolation
- Smooth budget sparklines using shared monotone_subdivide function
- Add vertical spacing to budget rows
- Add app icon (receipt on GNOME blue) in all sizes for desktop, web, and AppImage
- Add calendar, credit cards, forecast, goals, insights, and wishlist views
- Add date picker, numpad, quick-add, category combo, and edit dialog components
- Add import/export for CSV, JSON, OFX, QIF formats
- Add NLP transaction parsing, OCR receipt scanning, expression evaluator
- Add notification support, Sankey chart, tray icon
- Add demo data seeder with full DB wipe
- Expand database schema with subscriptions, goals, credit cards, and more

outlay-gtk/src/calendar_view.rs

@@ -0,0 +1,168 @@
+use gtk::prelude::*;
+use chrono::{Datelike, NaiveDate};
+use outlay_core::db::Database;
+
+/// Create a spending heatmap calendar for a given month.
+pub fn calendar_heatmap(db: &Database, year: i32, month: u32) -> gtk::Box {
+    let container = gtk::Box::new(gtk::Orientation::Vertical, 8);
+
+    let raw_daily = db.get_daily_totals(year, month).unwrap_or_default();
+    // Extract (day_number, expense_amount)
+    let daily: Vec<(u32, f64)> = raw_daily.iter()
+        .map(|(date, _income, expense)| (date.day(), *expense))
+        .collect();
+    let max_val = daily.iter().map(|(_, v)| *v).fold(0.0_f64, f64::max);
+
+    // Day labels
+    let header = gtk::Box::new(gtk::Orientation::Horizontal, 2);
+    header.set_halign(gtk::Align::Center);
+    for day_name in &["Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"] {
+        let label = gtk::Label::new(Some(day_name));
+        label.set_width_chars(5);
+        label.add_css_class("caption");
+        label.add_css_class("dim-label");
+        header.append(&label);
+    }
+    container.append(&header);
+
+    // Build daily amount map
+    let mut amounts = std::collections::HashMap::new();
+    for (day, amount) in &daily {
+        amounts.insert(*day, *amount);
+    }
+
+    // Determine first day of month and number of days
+    let first_day = NaiveDate::from_ymd_opt(year, month, 1).unwrap();
+    let days_in_month = if month == 12 {
+        NaiveDate::from_ymd_opt(year + 1, 1, 1)
+    } else {
+        NaiveDate::from_ymd_opt(year, month + 1, 1)
+    }.and_then(|d| d.pred_opt()).map(|d| d.day()).unwrap_or(30);
+
+    // Monday = 0, Sunday = 6
+    let first_weekday = first_day.weekday().num_days_from_monday();
+
+    let grid = gtk::Grid::new();
+    grid.set_row_spacing(2);
+    grid.set_column_spacing(2);
+    grid.set_halign(gtk::Align::Center);
+
+    let mut day = 1_u32;
+    let mut row = 0;
+    let mut col = first_weekday as i32;
+
+    while day <= days_in_month {
+        let amount = amounts.get(&day).copied().unwrap_or(0.0);
+        let cell = make_cell(day, amount, max_val);
+        grid.attach(&cell, col, row, 1, 1);
+
+        col += 1;
+        if col > 6 {
+            col = 0;
+            row += 1;
+        }
+        day += 1;
+    }
+
+    container.append(&grid);
+
+    // Legend
+    let legend = gtk::Box::new(gtk::Orientation::Horizontal, 4);
+    legend.set_halign(gtk::Align::Center);
+    legend.set_margin_top(4);
+
+    let less_label = gtk::Label::new(Some("Less"));
+    less_label.add_css_class("caption");
+    less_label.add_css_class("dim-label");
+    legend.append(&less_label);
+
+    for level in 0..5 {
+        let cell = gtk::DrawingArea::new();
+        cell.set_size_request(16, 16);
+        let intensity = level as f64 / 4.0;
+        cell.set_draw_func(move |_area, ctx, w, h| {
+            let (r, g, b, a) = intensity_color(intensity);
+            ctx.set_source_rgba(r, g, b, a);
+            let radius = 3.0;
+            let w = w as f64;
+            let h = h as f64;
+            ctx.new_sub_path();
+            ctx.arc(w - radius, radius, radius, -std::f64::consts::FRAC_PI_2, 0.0);
+            ctx.arc(w - radius, h - radius, radius, 0.0, std::f64::consts::FRAC_PI_2);
+            ctx.arc(radius, h - radius, radius, std::f64::consts::FRAC_PI_2, std::f64::consts::PI);
+            ctx.arc(radius, radius, radius, std::f64::consts::PI, 3.0 * std::f64::consts::FRAC_PI_2);
+            ctx.close_path();
+            let _ = ctx.fill();
+        });
+        legend.append(&cell);
+    }
+
+    let more_label = gtk::Label::new(Some("More"));
+    more_label.add_css_class("caption");
+    more_label.add_css_class("dim-label");
+    legend.append(&more_label);
+
+    container.append(&legend);
+    container
+}
+
+fn make_cell(day: u32, amount: f64, max_val: f64) -> gtk::DrawingArea {
+    let cell = gtk::DrawingArea::builder()
+        .accessible_role(gtk::AccessibleRole::Img)
+        .build();
+    cell.set_size_request(44, 44);
+
+    let intensity = if max_val > 0.0 { amount / max_val } else { 0.0 };
+    let day_str = format!("{}", day);
+    let has_spending = amount > 0.0;
+    let tooltip = if has_spending {
+        format!("Day {}: {:.2}", day, amount)
+    } else {
+        format!("Day {}: no spending", day)
+    };
+    cell.set_tooltip_text(Some(&tooltip));
+    cell.update_property(&[gtk::accessible::Property::Label(&tooltip)]);
+
+    cell.set_draw_func(move |_area, ctx, w, h| {
+        let w = w as f64;
+        let h = h as f64;
+
+        // Background with rounded corners
+        let radius = 4.0;
+        let (r, g, b, a) = intensity_color(intensity);
+        ctx.set_source_rgba(r, g, b, a);
+        ctx.new_sub_path();
+        ctx.arc(w - radius, radius, radius, -std::f64::consts::FRAC_PI_2, 0.0);
+        ctx.arc(w - radius, h - radius, radius, 0.0, std::f64::consts::FRAC_PI_2);
+        ctx.arc(radius, h - radius, radius, std::f64::consts::FRAC_PI_2, std::f64::consts::PI);
+        ctx.arc(radius, radius, radius, std::f64::consts::PI, 3.0 * std::f64::consts::FRAC_PI_2);
+        ctx.close_path();
+        let _ = ctx.fill();
+
+        // Day number
+        ctx.set_source_rgba(1.0, 1.0, 1.0, if has_spending { 0.9 } else { 0.5 });
+        ctx.select_font_face("sans-serif", gtk::cairo::FontSlant::Normal, gtk::cairo::FontWeight::Normal);
+        ctx.set_font_size(12.0);
+        let extents = ctx.text_extents(&day_str).unwrap();
+        let x = (w - extents.width()) / 2.0 - extents.x_bearing();
+        let y = (h - extents.height()) / 2.0 - extents.y_bearing();
+        ctx.move_to(x, y);
+        let _ = ctx.show_text(&day_str);
+    });
+
+    cell
+}
+
+fn intensity_color(intensity: f64) -> (f64, f64, f64, f64) {
+    if intensity <= 0.0 {
+        (0.5, 0.5, 0.5, 0.1)
+    } else if intensity < 0.25 {
+        (0.42, 0.75, 0.45, 0.4)
+    } else if intensity < 0.5 {
+        (0.85, 0.75, 0.35, 0.5)
+    } else if intensity < 0.75 {
+        (0.87, 0.55, 0.33, 0.6)
+    } else {
+        (0.87, 0.33, 0.36, 0.7)
+    }
+}