chore: scaffold moments workspace

Cargo workspace with five crates per architecture conventions:

- moments-entities: Source enum, Event, EventQuery, SourceSummary
- moments-core:     EventReader / EventWriter ports
- moments-data:     PgStore (sqlx postgres adapter) + 0001_init.sql
- moments-api:      axum binary; /v1/{healthz,events,sources}
- moments-worker:   skeleton; pollers land in step 2

Sources committed-to for ingestion: github, gitea, hg, bugzilla.
Workstation events explicitly retired (not deferred).

Build + clippy clean. sqlx queries use the runtime API for now;
will switch to compile-time-checked macros + .sqlx offline cache
once magrathea has the moments_{ro,rw} roles and database created.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

crates/moments-worker/src/main.rs

@@ -0,0 +1,37 @@
+use clap::Parser;
+use moments_data::PgStore;
+use tracing::info;
+
+#[derive(Parser, Debug)]
+#[command(version, about = "moments ingestion worker")]
+struct Args {
+    #[arg(long, env = "DATABASE_URL")]
+    database_url: String,
+}
+
+#[tokio::main]
+async fn main() -> anyhow::Result<()> {
+    init_tracing();
+    let args = Args::parse();
+
+    let store = PgStore::connect(&args.database_url).await?;
+    store.migrate().await?;
+
+    info!("worker started — pollers will land in step 2");
+
+    // Pollers (github, gitea, hg, bugzilla) land in subsequent steps.
+    // For now this binary only verifies it can reach the database.
+    let _ = store;
+    Ok(())
+}
+
+fn init_tracing() {
+    use tracing_subscriber::{EnvFilter, fmt};
+    let filter = EnvFilter::try_from_default_env().unwrap_or_else(|_| EnvFilter::new("info"));
+    let json = std::env::var("JOURNAL_STREAM").is_ok();
+    if json {
+        fmt().with_env_filter(filter).json().init();
+    } else {
+        fmt().with_env_filter(filter).init();
+    }
+}