docs: document `zamsync project` in README with usage examples

[Etoile-Bleu]

Summary

The zamsync project command was added in Phase 11 but the README does not mention it yet. A new contributor can fill this gap with a pure documentation change -- no Rust required.

Context and motivation

zamsync project reads the local WAL and inserts events into a SQLite database, making them queryable with standard SQL tools. Anyone evaluating ZamSync for a real deployment will want to know this exists.

Exact task

Add a "Projecting to SQLite" section to README.md, after the existing "CLI Quick Start" section. It should cover:

1. Basic usage: zamsync project <data-dir>
2. Custom output path: zamsync project <data-dir> --target sqlite://path/to/output.db
3. Dry run: zamsync project <data-dir> --dry-run
4. Batch size tuning: --batch-size 500
5. Expected output format (lines like 3 projected, 0 already present)

Acceptance criteria

• README renders correctly on GitHub (check with a local Markdown previewer)
• All flags shown match what zamsync project --help actually prints
• No em dashes (-- not -- in prose; use hyphens for flags)

Estimated effort

~1 h -- small (one function, one test)