Phase 17: profile level-up system

XP thresholds (500→1200→2000→…→11000→+2500/level) drive automatic level
increases. add_xp_with_levelup() replaces bare add_xp() in match
processing: for each level gained it grants level×500 coins and milestone
packs (bronze@5, silver@10, gold@15, rare_gold@20, gold every 5 after).

GET /profile now returns computed level (recalculated from XP so it
stays consistent), xp_to_next_level, and xp_for_next_level so the
dashboard can render a progress bar without a second call.

POST /matches/result response gains level_ups array (empty when no
level-up occurred) with new_level, coins_granted, pack_granted per event.

Four new tests: profile level fields, level_for_xp boundary checks,
level-up event in match result, milestone pack unit test.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/services/profile.rs

@@ -1,7 +1,7 @@
 use crate::{
     db::Pool,
     error::{AppError, AppResult},
-    models::profile::Profile,
+    models::profile::{coins_for_level, level_for_xp, pack_for_level, LevelUpEvent, Profile},
 };
 use chrono::Utc;
 
@@ -50,3 +50,44 @@ pub async fn add_xp(pool: &Pool, profile_id: &str, xp: i64) -> AppResult<()> {
         .await?;
     Ok(())
 }
+
+/// Add XP, check for level-ups, grant rewards, and return every level gained.
+/// Callers should use this instead of `add_xp` when level-up feedback matters.
+pub async fn add_xp_with_levelup(
+    pool: &Pool,
+    profile_id: &str,
+    club_id: &str,
+    xp_to_add: i64,
+) -> AppResult<Vec<LevelUpEvent>> {
+    let profile = get_active_profile(pool).await?;
+    let old_level = level_for_xp(profile.xp);
+    let new_total_xp = profile.xp + xp_to_add;
+    let new_level = level_for_xp(new_total_xp);
+
+    let now = Utc::now();
+    sqlx::query("UPDATE profiles SET xp = ?, level = ?, updated_at = ? WHERE id = ?")
+        .bind(new_total_xp)
+        .bind(new_level)
+        .bind(now)
+        .bind(profile_id)
+        .execute(pool)
+        .await?;
+
+    let mut events = Vec::new();
+    for lvl in (old_level + 1)..=new_level {
+        let coins = coins_for_level(lvl);
+        let pack = pack_for_level(lvl).map(String::from);
+
+        if coins > 0 {
+            crate::services::club::add_coins(pool, club_id, coins).await?;
+        }
+        if let Some(ref pack_id) = pack {
+            crate::services::pack::grant_pack(pool, club_id, pack_id).await?;
+        }
+
+        tracing::info!(profile_id, new_level = lvl, coins, "level up");
+        events.push(LevelUpEvent { new_level: lvl, coins_granted: coins, pack_granted: pack });
+    }
+
+    Ok(events)
+}