Split renovate config: repo config in renovate.json, bot config in ops/

Renovate liest die repo-eigene renovate.json als REPO-Config, nicht
als BOT-Config. Bot-spezifische Felder (platform, endpoint,
repositories, autodiscover, gitAuthor, prHourlyLimit, ...) gehoeren
nicht hinein und werden als "this repo is forbidden / disabled"
fehlinterpretiert.

Saubere Trennung:
- renovate.json (Repo-Root): nur extends, packageRules,
  ignorePaths, manager file patterns, labels, rangeStrategy
- ops/renovate/bot-config.js: Plattform, Endpoint, Username,
  gitAuthor, autodiscover=false, repositories=[Micha/homelab-infra],
  Concurrent-/Hourly-Limits

bot-config.js statt config.json, weil Renovate Module-exports als
config-file akzeptiert (offizielle Variante).

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

renovate.json

@@ -5,18 +5,7 @@
     ":dependencyDashboard",
     ":semanticCommits"
   ],
-  "platform": "gitea",
-  "endpoint": "https://git.kaleschke.info/api/v1",
-  "username": "renovate",
-  "gitAuthor": "Renovate Bot <renovate@kaleschke.info>",
-  "onboarding": false,
-  "requireConfig": "optional",
-  "autodiscover": false,
-  "repositories": ["Micha/homelab-infra"],
   "dependencyDashboardTitle": "Renovate Dependency Dashboard",
-  "prHourlyLimit": 0,
-  "prConcurrentLimit": 5,
-  "branchConcurrentLimit": 10,
   "labels": ["dependencies"],
   "rangeStrategy": "pin",
   "lockFileMaintenance": {