Create postgres project scaffold on local init

[sdairs]

Summary

Closes #221.

local init previously only created the clickhouse/ project scaffold. It now also creates a postgres/ scaffold so Postgres project files have a home.

The Postgres scaffold is PG-native rather than a mirror of the ClickHouse one: plain views/ and functions/ (procedures) are far more central to a Postgres project than ClickHouse-style materialized views — in Postgres a materialized view is just a manually-refreshed query snapshot, not an insert-time pipeline.

clickhouse/
├── tables/
├── materialized_views/
├── queries/
└── seed/
postgres/
├── tables/
├── views/
├── functions/
├── queries/
└── seed/

Each subdir gets a .gitkeep.

Changes

• init.rs: added postgres_project_dir(); generalized create_project_scaffold to take an explicit target dir + subdirs and call it for both engines.
• Added unit tests covering scaffold creation (dirs + .gitkeep) and idempotency.
• Updated the local init agent help text and README.md.

Testing

• cargo test -p clickhousectl
• cargo clippy -p clickhousectl

🤖 Generated with Claude Code

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Note

Low Risk
Filesystem-only init scaffolding and docs; no runtime server, auth, or data-path behavior changes.

Overview
clickhousectl local init now scaffolds a committed postgres/ tree alongside the existing clickhouse/ layout, so Postgres SQL assets have a standard home next to ClickHouse project files.

Scaffold creation is refactored: create_project_scaffold takes a target directory and subdirectory list and is invoked twice—clickhouse/ keeps tables, materialized_views, queries, seed; postgres/ gets tables, views, functions, queries, seed (each with .gitkeep). postgres_project_dir() was added for the new root. Unit tests cover directory/.gitkeep creation and idempotent re-runs. README and local init agent help text document both trees.

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