feat: Phase 2 — user experience & advanced filtering

- Add price_min/price_max filters per keyword (stored in cents)
- Add allowed_postcodes filter per keyword (text[] array)
- Add mute hours per user with cross-midnight support
- Add digest mode with configurable interval and buffered summaries
- 10 new bot commands: /price_min, /price_max, /clear_price, /postcode,
  /clear_postcode, /mute_hours, /mute_off, /digest_on, /digest_off, /status
- Updated keyword card display to show price range and postcodes
- New migrations: 05-keyword-filters.sql, 06-user-settings.sql

worker/src/migrations/05-keyword-filters.sql

@@ -0,0 +1,9 @@
+-- Phase 2: Price and postcode filters per keyword
+ALTER TABLE keywords 
+    ADD COLUMN IF NOT EXISTS price_min int,
+    ADD COLUMN IF NOT EXISTS price_max int,
+    ADD COLUMN IF NOT EXISTS allowed_postcodes text[];
+
+COMMENT ON COLUMN keywords.price_min IS 'Minimum price in cents (e.g. 5000 = €50). NULL = no limit.';
+COMMENT ON COLUMN keywords.price_max IS 'Maximum price in cents (e.g. 500000 = €5000). NULL = no limit.';
+COMMENT ON COLUMN keywords.allowed_postcodes IS 'Austrian postcodes (4-digit strings). Only ads matching these are notified.';

worker/src/migrations/06-user-settings.sql

@@ -0,0 +1,31 @@
+-- Phase 2: User settings (mute hours + digest mode) and digest buffer
+CREATE TABLE IF NOT EXISTS user_settings (
+    telegram_id       text PRIMARY KEY,
+    mute_start        time,
+    mute_end          time,
+    digest_mode       bool NOT NULL DEFAULT false,
+    digest_interval   int NOT NULL DEFAULT 60,
+    last_digest_flush timestamptz,
+    CONSTRAINT chk_mute_hours CHECK (
+        mute_start IS NULL AND mute_end IS NULL 
+        OR mute_start IS NOT NULL AND mute_end IS NOT NULL
+    )
+);
+
+COMMENT ON TABLE user_settings IS 'User-specific settings for notification behavior';
+
+CREATE TABLE IF NOT EXISTS digest_buffer (
+    id          uuid PRIMARY KEY DEFAULT gen_random_uuid(),
+    telegram_id text NOT NULL,
+    ad_id       uuid REFERENCES ads(id) ON DELETE CASCADE,
+    keyword     text NOT NULL,
+    title       text NOT NULL,
+    price       int,  -- in cents
+    url         text,
+    created_at  timestamptz NOT NULL DEFAULT now()
+);
+
+CREATE INDEX IF NOT EXISTS idx_digest_buffer 
+    ON digest_buffer(telegram_id, created_at DESC);
+
+COMMENT ON TABLE digest_buffer IS 'Buffer for digest-mode notifications, flushed at intervals';