fix(multiplayer): wire a durable RankedProfileProvider

Same discovery pattern as ResultSubmitter/SessionIssuer, one level
deeper: api.Service.rankedProfile and .profile both only ever read
from an in-memory RankedProfiles map with no durable-store equivalent
at all -- not "adapter exists but unwired" this time, there was no
adapter. Every real request to GET /v1/profile/ranked or /api/v1/profile
always 404'd regardless of a player's actual rating.

Add RankedProfileProvider (an interface, not a struct-literal adapter
this time) and store.PostgresRankedProfiles reading the ratings table;
Service.rankedProfileFor prefers it when set and falls back to the
map otherwise, so every existing test/direct Service literal keeps
compiling and passing unchanged. A missing ratings row maps to the
exact same (zero value, false, nil) the map lookup already produced,
preserving existing not-found semantics rather than reinterpreting
them. LastSeasonID/SeasonHistory are deliberately left unset -- the
ratings table has no season pointer, and reconstructing history needs
its own query and display semantics, not bundled in here speculatively.

Wired into both cmd/control-plane and cmd/testkit-api. Verified
against real PostgreSQL via curl: a fresh identity's ranked profile
correctly 404s through the real adapter (same behavior as before,
now for a real reason instead of an empty map).

server/store/ranked_profile_sql.go

@@ -0,0 +1,43 @@
+package store
+
+import (
+	"context"
+	"database/sql"
+	"fmt"
+
+	"github.com/cosmic-clash/cosmic-clash/server/domain"
+)
+
+const RankedProfileSelectSQL = `SELECT rating, deviation, volatility, ranked_games, updated_at
+FROM ratings
+WHERE player_id = $1`
+
+// PostgresRankedProfiles reads the durable rating row api.Service's
+// RankedProfileProvider needs. A missing row means "this player has no
+// ranked profile yet" (never queued ranked, or their identity predates any
+// result) -- that's a real, expected state, not an error, and is reported
+// the same way the in-memory RankedProfiles map api.Service still falls
+// back to already did: (zero value, false, nil).
+//
+// LastSeasonID and SeasonHistory are deliberately left at their zero values.
+// The ratings table has no "current season" column, and reconstructing
+// season history means a second query against ranked_season_rollovers with
+// its own display semantics to settle -- a real, separate piece of work,
+// not bundled into this read path speculatively.
+type PostgresRankedProfiles struct{ DB *sql.DB }
+
+func (p PostgresRankedProfiles) Get(ctx context.Context, playerID string) (domain.RankedProfile, bool, error) {
+	if p.DB == nil || playerID == "" {
+		return domain.RankedProfile{}, false, fmt.Errorf("invalid ranked profile lookup")
+	}
+	var profile domain.RankedProfile
+	err := p.DB.QueryRowContext(ctx, RankedProfileSelectSQL, playerID).
+		Scan(&profile.Value, &profile.RD, &profile.Volatility, &profile.RankedGames, &profile.LastRatedAt)
+	if err == sql.ErrNoRows {
+		return domain.RankedProfile{}, false, nil
+	}
+	if err != nil {
+		return domain.RankedProfile{}, false, err
+	}
+	return profile, true, nil
+}