feat: replace Web Push with ntfy for medication reminders

Single notification path via ntfy HTTP publish for reliable Android delivery;
remove VAPID, push subscriptions, and SW push handlers. PWA settings show
topic subscribe link; humor texts and deep-link actions unchanged.

Co-authored-by: Cursor <cursoragent@cursor.com>

tools/schema.sql

@@ -10,14 +10,6 @@ CREATE TABLE IF NOT EXISTS intake_log (
 CREATE INDEX IF NOT EXISTS idx_intake_day ON intake_log(day);
 CREATE INDEX IF NOT EXISTS idx_intake_slot_day ON intake_log(slot_id, day);
 
-CREATE TABLE IF NOT EXISTS push_subscription (
-  id INTEGER PRIMARY KEY AUTOINCREMENT,
-  endpoint TEXT UNIQUE NOT NULL,
-  p256dh TEXT NOT NULL,
-  auth TEXT NOT NULL,
-  created_at TEXT NOT NULL
-);
-
 CREATE TABLE IF NOT EXISTS ai_cache (
   key TEXT PRIMARY KEY,
   content TEXT NOT NULL,