Add link editing, AI re-description, and footer

Links can now be edited manually (title, summary, category,
manufacturer, tags) via an inline edit form, with a "KI neu
beschreiben lassen" action that re-fetches the URL and lets the AI
regenerate all fields. Editing recomputes the search embedding.

Also adds an app footer showing author, version, and hostname.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

app/config.py

@@ -1,9 +1,14 @@
 import os
+import socket
 
 from dotenv import load_dotenv
 
 load_dotenv()
 
+APP_AUTHOR = "Erik Thiele"
+APP_VERSION = os.getenv("APP_VERSION", "1.0.0")
+APP_HOST = socket.gethostname()
+
 SECRET_KEY = os.getenv("SECRET_KEY", "dev-insecure-secret-change-me")
 OPENAI_API_KEY = os.getenv("OPENAI_API_KEY", "").strip()
 OPENAI_MODEL = os.getenv("OPENAI_MODEL", "gpt-4o-mini")