Auto-route inbox imports to configured accounts

[codeforester]

Summary

Allow bank-buddy import inbox to import files without --account-id when the parser can reliably infer the configured account from statement metadata.

Scope

• Auto-route Bank of America PDF files by extracting the full account number and matching it to accounts.account_number.
• Keep --account-id as an explicit override/guard.
• Leave ambiguous or unsupported files in the inbox with clear per-file messages.
• Keep BOA CSV imports explicit unless reliable account metadata is available.
• Update tests and docs for the new command behavior.

Validation

• uv run pytest
• ./tests/validate.sh