feat(match): atomic exactly-once match-completion transaction

Add complete_match: one BEGIN/COMMIT that validates identity + result,
enforces a durable (profile_id, match_identity) uniqueness guard
(migration 0022 match_completions), persists match history, and grants
coins + XP/level-ups + W/D/L/DNF statistics + objectives + achievements
exactly once. Any failure rolls the whole match back (no compensating
cleanup). Handles sequential/restart/concurrent replay, conflicting
re-report (first result canonical), DNF (loss economics, own stat
bucket) and no-contest (zero economic effect).

Adds tx-scoped variants: statistics::record_match_tx/
record_position_goals_tx, objective::increment_metric_tx,
achievement::check_and_unlock_tx. New MatchResultKind/CompleteMatchRequest/
MatchCompletionResult models + POST /matches/complete route.

src/models/match_result.rs

@@ -11,6 +11,45 @@ pub enum MatchOutcome {
     Loss,
 }
 
+/// Canonical, game-independent economic result of a completed match. The game
+/// adapter maps its own wire (FIFA17 `endReason`, score, …) onto this — Core
+/// never sees a game-specific reason string.
+///
+/// * `Win` / `Draw` / `Loss` — a finished match; standard reward tiers.
+/// * `Dnf` — did-not-finish (abandon/quit). Economically a loss, but tallied in
+///   its own statistics bucket and never in `matches_lost`.
+/// * `NoContest` — a voided match. Zero economic effect: no coins, XP, or
+///   W/D/L/DNF change; recorded only for history + idempotency.
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[serde(rename_all = "snake_case")]
+pub enum MatchResultKind {
+    Win,
+    Draw,
+    Loss,
+    Dnf,
+    NoContest,
+}
+
+impl MatchResultKind {
+    /// The canonical lowercase token persisted in `matches.outcome` and
+    /// `match_completions.result`.
+    pub fn as_str(self) -> &'static str {
+        match self {
+            MatchResultKind::Win => "win",
+            MatchResultKind::Draw => "draw",
+            MatchResultKind::Loss => "loss",
+            MatchResultKind::Dnf => "dnf",
+            MatchResultKind::NoContest => "no_contest",
+        }
+    }
+
+    /// Whether this result applies any economic effect (coins / XP / statistics /
+    /// objectives / achievements). `NoContest` is the only non-economic result.
+    pub fn is_economic(self) -> bool {
+        !matches!(self, MatchResultKind::NoContest)
+    }
+}
+
 #[derive(Debug, Deserialize)]
 pub struct SubmitMatchRequest {
     pub squad_id: String,
@@ -87,3 +126,44 @@ pub struct MatchRewardResult {
     /// Achievements unlocked as a result of this match.
     pub achievements_unlocked: Vec<AchievementDefinition>,
 }
+
+/// Request to atomically complete a match exactly once. `match_identity` is the
+/// opaque, host-supplied per-match token that keys durable economic idempotency
+/// (persona/profile + match_identity). `result` is the canonical outcome the
+/// game adapter derived from its wire; `goals_for`/`goals_against` are recorded
+/// for history and statistics (0-0 is normal for a DNF/no-contest).
+#[derive(Debug, Clone, Deserialize)]
+pub struct CompleteMatchRequest {
+    pub match_identity: String,
+    pub result: MatchResultKind,
+    pub squad_id: String,
+    pub opponent_name: String,
+    pub goals_for: i64,
+    pub goals_against: i64,
+    pub mode: String,
+    #[serde(default)]
+    pub goal_positions: Option<Vec<String>>,
+}
+
+/// Outcome of [`crate::services::match_service::complete_match`].
+#[derive(Debug, Serialize)]
+pub struct MatchCompletionResult {
+    /// `true` when THIS call applied the economic effect; `false` on an
+    /// idempotent replay of an already-completed match (the persisted canonical
+    /// result is echoed unchanged).
+    pub applied: bool,
+    pub match_identity: String,
+    pub result: MatchResultKind,
+    pub coins_awarded: i64,
+    pub xp_awarded: i64,
+    /// Club balance after completion — echoed so the host can render the wire
+    /// reward body without a second round-trip.
+    pub coins_balance: i64,
+    /// Objectives completed by this match (empty on a replay).
+    pub objectives_updated: Vec<String>,
+    /// Level-ups gained from this match's XP (empty on a replay).
+    pub level_ups: Vec<LevelUpEvent>,
+    /// Achievements unlocked by this match (empty on a replay).
+    pub achievements_unlocked: Vec<AchievementDefinition>,
+    pub match_record: Match,
+}