feat: add SQLite support, setup wizard enhancements, and live dashboard

Add zero-dependency SQLite mode so users can run Erupe without
PostgreSQL. A transparent db.DB wrapper auto-translates PostgreSQL
SQL ($N placeholders, now(), ::casts, ILIKE, public. prefix,
TRUNCATE) for SQLite at runtime — all 28 repo files use the wrapper
with no per-query changes needed.

Setup wizard gains two new steps: quest file detection with download
link, and gameplay presets (solo/small/community/rebalanced). The API
server gets a /dashboard endpoint with auto-refreshing stats.

CI release workflow now builds and pushes Docker images to GHCR
alongside binary artifacts on tag push.

Key changes:
- common/db: DB/Tx wrapper with 6 SQL translation rules
- server/migrations/sqlite: full SQLite schema (0001-0005)
- config: Database.Driver field ("postgres" or "sqlite")
- main.go: SQLite connection with WAL mode, single writer
- server/setup: quest check + preset selection steps
- server/api: /dashboard with live stats
- .github/workflows: Docker in release, deduplicate docker.yml

common/db/adapter_test.go

@@ -0,0 +1,83 @@
+package db
+
+import (
+	"testing"
+)
+
+func TestAdaptSQL(t *testing.T) {
+	tests := []struct {
+		name  string
+		input string
+		want  string
+	}{
+		{
+			name:  "placeholder rebind",
+			input: "SELECT * FROM users WHERE id=$1 AND name=$2",
+			want:  "SELECT * FROM users WHERE id=? AND name=?",
+		},
+		{
+			name:  "now() replacement",
+			input: "UPDATE characters SET guild_post_checked=now() WHERE id=$1",
+			want:  "UPDATE characters SET guild_post_checked=CURRENT_TIMESTAMP WHERE id=?",
+		},
+		{
+			name:  "type cast removal",
+			input: "UPDATE users SET frontier_points=frontier_points::int - $1 WHERE id=$2 RETURNING frontier_points",
+			want:  "UPDATE users SET frontier_points=frontier_points - ? WHERE id=? RETURNING frontier_points",
+		},
+		{
+			name:  "text cast removal",
+			input: "SELECT COALESCE(friends, ''::text) FROM characters WHERE id=$1",
+			want:  "SELECT COALESCE(friends, '') FROM characters WHERE id=?",
+		},
+		{
+			name:  "timestamptz cast removal",
+			input: "SELECT COALESCE(created_at, '2000-01-01'::timestamptz) FROM guilds WHERE id=$1",
+			want:  "SELECT COALESCE(created_at, '2000-01-01') FROM guilds WHERE id=?",
+		},
+		{
+			name:  "ILIKE to LIKE",
+			input: "SELECT * FROM characters WHERE name ILIKE $1",
+			want:  "SELECT * FROM characters WHERE name LIKE ?",
+		},
+		{
+			name:  "character varying cast",
+			input: "DEFAULT ''::character varying",
+			want:  "DEFAULT ''",
+		},
+		{
+			name:  "no changes for standard SQL",
+			input: "SELECT COUNT(*) FROM users",
+			want:  "SELECT COUNT(*) FROM users",
+		},
+		{
+			name:  "NOW uppercase",
+			input: "INSERT INTO events (start_time) VALUES (NOW())",
+			want:  "INSERT INTO events (start_time) VALUES (CURRENT_TIMESTAMP)",
+		},
+		{
+			name:  "multi-digit params",
+			input: "INSERT INTO t (a,b,c) VALUES ($1,$2,$10)",
+			want:  "INSERT INTO t (a,b,c) VALUES (?,?,?)",
+		},
+		{
+			name:  "public schema prefix",
+			input: "INSERT INTO public.distributions_accepted VALUES ($1, $2)",
+			want:  "INSERT INTO distributions_accepted VALUES (?, ?)",
+		},
+		{
+			name:  "TRUNCATE to DELETE FROM",
+			input: "TRUNCATE public.cafebonus;",
+			want:  "DELETE FROM cafebonus;",
+		},
+	}
+
+	for _, tc := range tests {
+		t.Run(tc.name, func(t *testing.T) {
+			got := AdaptSQL(tc.input)
+			if got != tc.want {
+				t.Errorf("\ngot:  %s\nwant: %s", got, tc.want)
+			}
+		})
+	}
+}