Introduce bb CLI and v2 source namespace

[codeforester]

Summary

Create a separate v2 source namespace and CLI so the new financial-intelligence implementation can evolve without disturbing the existing bankbuddy and taxbuddy code paths.

Scope

• Move the new v2 DAO/record code under a dedicated bankbuddy.bb package.
• Add a new bb CLI entrypoint for v2 workflows.
• Keep existing bankbuddy and taxbuddy CLI entrypoints unchanged.
• Add minimal bb status/schema output that proves the CLI reads the additive BB_ foundation tables.
• Update docs/context to describe the side-by-side migration approach.

Out of scope

• Migrating existing banking importers to BB_ tables.
• Removing legacy source files or legacy SQLite tables.
• User-facing infer workflows.

Acceptance criteria

• uv run bb status works.
• Existing uv run bankbuddy status and uv run taxbuddy status entrypoints remain configured.
• New v2 imports use bankbuddy.bb, not bankbuddy.financial.
• Tests prove the bb CLI and package separation.
• Validation passes.

Follows #122.