Fix Anki integration to support non-English environments and custom models

[ShengWang1017]

Problem

The extension only worked with English Anki installations using the "Basic" model with "Front"/"Back" fields,
failing for users with:

• Non-English Anki (Chinese, Japanese, etc.)
• Custom note types
• Different field names

Solution

• Auto-detect compatible models: Scans all available note types and tests compatibility by creating/deleting test
  cards
• Language-agnostic: Works with any field names in any language
• Smart fallback: Prefers Front/Back fields but falls back to first two fields of any model
• Better error handling: Clear error messages when no compatible model is found

Changes

• Added findCompatibleModel() to automatically discover usable note types
• Added testModelCompatibility() to verify models work before use
• Removed hardcoded "Basic" model and "Front"/"Back" field names
• Added duplicate prevention with allowDuplicate: false

Testing

Tested with:

• ✅ English Anki (Basic model)
• ✅ Chinese Anki (基础 model)

Fixes #272

[Nitrino]

Hey @ShengWang1017. Thanks for your contribution, this is a really useful change, I will do a review soon

[ShengWang1017]

Hi @Nitrino . If need any help, please let me know.