Add Telegram cancellation import functionality with tests and documentation

- Implemented Telegram cancellation parsing logic in `telegramCancellationParser.js`.
- Created unit tests for cancellation parsing in `telegramCancellationParser.test.js`.
- Developed integration tests for Telegram import service in `telegramImport.integration.test.js`.
- Added API tests for Telegram import endpoints in `telegramImportApi.test.js`.
- Introduced service tests for Telegram import logic in `telegramImportService.test.js`.
- Documented the Telegram cancellation import process in `telegram-cancellation-import.md`.
- Built a React component for managing Telegram imports in `TelegramImportPanel.jsx`.

backend/migrations/013_telegram_alert_import.sql

@@ -0,0 +1,45 @@
+-- Admin alert forms already store UTC clock values. Give these columns an
+-- explicit timezone so imports, API serialization and midnight expiry agree
+-- regardless of the PostgreSQL or Node.js host timezone. Safe to rerun.
+DO $$
+DECLARE col text;
+BEGIN
+  FOREACH col IN ARRAY ARRAY['start_time', 'end_time', 'created_at'] LOOP
+    IF EXISTS (SELECT 1 FROM information_schema.columns
+      WHERE table_schema = current_schema() AND table_name = 'alerts'
+        AND column_name = col AND data_type = 'timestamp without time zone') THEN
+      EXECUTE format('ALTER TABLE alerts ALTER COLUMN %I TYPE timestamptz USING %I AT TIME ZONE ''UTC''', col, col);
+    END IF;
+  END LOOP;
+END $$;
+
+ALTER TABLE alerts ADD COLUMN IF NOT EXISTS notification_pending BOOLEAN NOT NULL DEFAULT false;
+
+CREATE TABLE IF NOT EXISTS telegram_import_messages (
+  id SERIAL PRIMARY KEY,
+  city_id INTEGER NOT NULL REFERENCES cities(id),
+  channel_id TEXT NOT NULL,
+  channel_username VARCHAR(32) NOT NULL,
+  message_id INTEGER NOT NULL CHECK (message_id > 0),
+  published_at TIMESTAMPTZ NOT NULL,
+  edited_at TIMESTAMPTZ,
+  content_hash CHAR(64) NOT NULL,
+  raw_text TEXT NOT NULL,
+  has_media BOOLEAN NOT NULL DEFAULT false,
+  status VARCHAR(20) NOT NULL CHECK (status IN ('review', 'published', 'dismissed', 'expired')),
+  reasons JSONB NOT NULL DEFAULT '[]',
+  parsed JSONB NOT NULL DEFAULT '{}',
+  reviewed_by INTEGER REFERENCES users(id) ON DELETE SET NULL,
+  created_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  updated_at TIMESTAMPTZ NOT NULL DEFAULT now(),
+  UNIQUE (city_id, channel_id, message_id)
+);
+
+CREATE TABLE IF NOT EXISTS telegram_import_alerts (
+  message_id INTEGER NOT NULL REFERENCES telegram_import_messages(id) ON DELETE CASCADE,
+  route_id INTEGER NOT NULL REFERENCES routes(id) ON DELETE CASCADE,
+  alert_id INTEGER UNIQUE REFERENCES alerts(id) ON DELETE SET NULL,
+  PRIMARY KEY (message_id, route_id)
+);
+
+CREATE INDEX IF NOT EXISTS idx_telegram_import_review ON telegram_import_messages(city_id, status, published_at DESC);