add features

backend/src/database/migrations/020_create_notifications.sql

@@ -0,0 +1,32 @@
+-- Migration 020: Create notifications table
+CREATE EXTENSION IF NOT EXISTS "uuid-ossp";
+
+CREATE TABLE IF NOT EXISTS notifications (
+    id          UUID PRIMARY KEY DEFAULT uuid_generate_v4(),
+    user_id     UUID NOT NULL REFERENCES users(id) ON DELETE CASCADE,
+    typ         VARCHAR(50)  NOT NULL,
+    titel       VARCHAR(500) NOT NULL,
+    nachricht   TEXT         NOT NULL,
+    schwere     VARCHAR(20)  NOT NULL DEFAULT 'info'
+                    CHECK (schwere IN ('info', 'warnung', 'fehler')),
+    gelesen     BOOLEAN      NOT NULL DEFAULT FALSE,
+    gelesen_am  TIMESTAMPTZ,
+    link        VARCHAR(500),
+    quell_id    VARCHAR(100),
+    quell_typ   VARCHAR(50),
+    erstellt_am TIMESTAMPTZ  NOT NULL DEFAULT NOW()
+);
+
+-- Fast lookup for unread badge count
+CREATE INDEX IF NOT EXISTS notifications_user_unread_idx
+    ON notifications (user_id, gelesen)
+    WHERE NOT gelesen;
+
+-- Fast lookup for notification list ordered by date
+CREATE INDEX IF NOT EXISTS notifications_user_date_idx
+    ON notifications (user_id, erstellt_am DESC);
+
+-- Dedup index: one unread notification per (user, source type, source id)
+CREATE UNIQUE INDEX IF NOT EXISTS notifications_dedup_idx
+    ON notifications (user_id, quell_typ, quell_id)
+    WHERE NOT gelesen AND quell_typ IS NOT NULL AND quell_id IS NOT NULL;