refactor: extract adapter-common crate — shared sqlx error mapping,

row-to-domain conversions, date/uuid utils

Eliminates 39 map_err copies, consolidates parse_uuid/parse_datetime/
datetime_to_str/format_year_month, extracts 7 shared row-to-domain
conversion functions (movie, review, watchlist, stats, user_summary).
Row structs stay per-adapter (FromRow is db-specific), only conversion
logic is shared. Net -281 lines.

crates/adapters/postgres/src/lib.rs

@@ -39,30 +39,6 @@ pub use watch_event::{PostgresWatchEventRepository, PostgresWebhookTokenReposito
 pub use watchlist::PostgresWatchlistRepository;
 pub use wrapup::{PostgresWrapUpRepository, PostgresWrapUpStatsQuery};
 
-pub(crate) fn format_year_month(ym: &str) -> String {
-    let parts: Vec<&str> = ym.splitn(2, '-').collect();
-    if parts.len() != 2 {
-        return ym.to_string();
-    }
-    let year = parts[0].get(2..).unwrap_or(parts[0]);
-    let month = match parts[1] {
-        "01" => "Jan",
-        "02" => "Feb",
-        "03" => "Mar",
-        "04" => "Apr",
-        "05" => "May",
-        "06" => "Jun",
-        "07" => "Jul",
-        "08" => "Aug",
-        "09" => "Sep",
-        "10" => "Oct",
-        "11" => "Nov",
-        "12" => "Dec",
-        _ => parts[1],
-    };
-    format!("{} '{}", month, year)
-}
-
 pub async fn migrate(pool: &PgPool) -> Result<(), DomainError> {
     sqlx::migrate!("./migrations")
         .set_ignore_missing(true)