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-core/src/bin/seed_demo.rs

@@ -0,0 +1,33 @@
+use std::path::PathBuf;
+
+fn main() {
+    let data_dir: PathBuf = dirs_next().join("outlay");
+    let db_path = data_dir.join("outlay.db");
+
+    println!("Database path: {}", db_path.display());
+
+    if db_path.exists() {
+        println!("Removing existing database for a clean seed...");
+        std::fs::remove_file(&db_path).expect("Failed to remove existing database");
+    }
+
+    let db = outlay_core::db::Database::open(&db_path)
+        .expect("Failed to open database");
+
+    println!("Seeding demo data (2 years of realistic usage)...");
+
+    outlay_core::seed::seed_demo_data(&db)
+        .expect("Failed to seed demo data");
+
+    println!("Done! Restart Outlay to see the demo data.");
+}
+
+fn dirs_next() -> PathBuf {
+    if let Ok(dir) = std::env::var("XDG_DATA_HOME") {
+        PathBuf::from(dir)
+    } else if let Ok(home) = std::env::var("HOME") {
+        PathBuf::from(home).join(".local").join("share")
+    } else {
+        PathBuf::from(".")
+    }
+}