feat: interactive CLI prompts for missing environment variables (#1610)

 Instead of failing with a clap error when required env vars are
  missing, the server now detects the storage subcommand and interactively
  prompts the user for each missing value. This covers:

  - Storage-specific envs (S3, Azure Blob, GCS)
  - TLS cert/key pair (detects partial config that would silently fall back to HTTP)
  - OIDC group (detects partial config where setting one var activates the whole group)
  - Kafka bootstrap servers, topics, and security credentials (feature-gated)

  Collected values are persisted to `.parseable.env` only after clap
  validation succeeds, so invalid entries are never saved. On subsequent
  startups, the file is auto-loaded (explicit env vars take precedence).
  The file is also `source`-able for shell-wide use.

  Interactive mode only activates when stdin is a terminal — non-interactive
  environments (Docker, CI) get the standard clap error as before. Secret
  fields (S3 secret key, SASL password, etc.) use hidden input via crossterm
  raw mode.

Author: nikhilsinhaparseable