feat: ✨ Implement Custom API Keys and Create Posts Route

[Dan6erbond]

Closes #26.

• Implement POST /api/keys handler to create user tokens with custom expiry and database entry.
• Implement user settings page to create API keys and manually revoke/set expiry.
• Implement POST /api/posts handler to create posts using custom token.
  • Introduces support for ShareX.

[Dan6erbond]

User Settings Page:

cURL Request to Create a Post:

curl -X POST \
  'http://localhost:8090/api/posts' \
  --header 'Accept: */*' \
  --header 'Authorization: Bearer <key>' \
  --form 'file=@/path/to/file.jpeg'

[cocogitto-bot[bot]]

:heavy_check_mark: 784ce15...c9734c0 - Conventional commits check succeeded.