Telegram-Kanaele als Quelle: Parser, Pipeline, UI-Checkbox, Validate-Endpoint

- Neuer source_type telegram_channel in models.py (Source + Incident)
- DB-Migration: include_telegram Spalte fuer incidents
- feeds/telegram_parser.py: Telethon-basierter Parser (analog RSS)
- Orchestrator: Telegram-Pipeline parallel zu RSS + WebSearch
- sources.py: POST /api/sources/telegram/validate Endpoint
- incidents.py: include_telegram in Create/Update/Response
- dashboard.html: Telegram-Checkbox + Filter-Option
- app.js: FormData, EditModal, SourceStats, TypeLabels
- config.py: TELEGRAM_API_ID, API_HASH, SESSION_PATH
- requirements.txt: telethon hinzugefuegt

requirements.txt

@@ -10,3 +10,4 @@ websockets
 python-multipart
 aiosmtplib
 geonamescache>=2.0
+telethon