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/adapter-common/Cargo.toml

@@ -0,0 +1,11 @@
+[package]
+name = "adapter-common"
+version = "0.1.0"
+edition = "2024"
+
+[dependencies]
+domain = { workspace = true }
+sqlx = { workspace = true }
+tracing = { workspace = true }
+chrono = { workspace = true }
+uuid = { workspace = true }