[Codex] 3.3: Integrate API-key flow into init command

[taariq]

Parent: #28

Depends on: #33, #34, #35, #36, #37 (Tasks 1.5, 2.1, 2.2, 3.1, 3.2)

Task

Integrate API-key flow into the init command in src/commands/init.rs.

File to Modify

src/commands/init.rs

What to Add

1. resolve_target_url() async function - Handles both connection string and API-key modes
2. Integration with interactive picker when in API-key mode
3. Call check_and_enable_logical_replication() when using API-key mode
4. Call create_missing_databases() when databases don't exist
5. Save target state after successful selection

See docs/plans/api-key-flow-implementation.md Task 3.3 for full code.

How to Test

# Test with explicit target (should work as before)
cargo run -- init --source "postgresql://localhost/test" --target "postgresql://localhost/target" --local

# Test with API key (should show interactive picker)
export SEREN_API_KEY=your_key
cargo run -- init --source "postgresql://localhost/test" --local

Commit Message

feat(init): Integrate API-key flow with interactive target selection

[taariq]

Implemented Task 3.3 by adding the target-mode resolver/interactive picker wiring in src/commands/init.rs, leveraging the CLI’s optional --target/--api-key arguments.

Highlights

• Added resolve_target_url to init.rs using serendb::resolve_target_mode, ConsoleClient, select_target, create_missing_databases, and persisted TargetState.
• When running with an API key, init now walks the interactive selection, enables logical replication, creates missing DBs, fetches a fresh connection string, and saves the target state for reuse.
• Falls back to saved state if available, warning when the source URL changes.
• Updated the main init flow in src/main.rs to call the resolver first, then pass the resolved URL + saved state through the existing local path.
• Verified with cargo build and cargo test serendb::client::tests -- --nocapture (remote integration test still failing due to unrelated upstream changes).