feat: seven-send 0.1.0 — Library + CLI für SMS und TTS-Anrufe via seven.io

Wiederverwendbarer Baustein (eigenes Paket), nutzbar in beliebigen Programmen,
Cron-Jobs und Alerts:

- client.py: synchroner SevenClient.send_sms / send_voice (Voice als SSML,
  XML-escaped); Result mit ok/code/price/error, best-effort Fehlerbehandlung,
  dry_run-Modus
- cli.py: `seven-send sms|voice` mit --dry-run, --json, sauberen Exit-Codes;
  API-Key aus --api-key oder $SEVEN_API_KEY
- src-Layout, pyproject (console_script seven-send), MIT-Lizenz
- 12 Tests (Client + CLI), httpx gemockt

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

LICENSE

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+MIT License
+
+Copyright (c) 2026 Dieter Schlüter
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.