feat(01-02): create Quill PostgreSQL context with ZIO integration

- Add QuillContext with dataSourceLayer and quillLayer
- Update application.conf for HikariCP-compatible format
- Export combined quillLive layer for database access

summercms/src/db/QuillContext.scala

@@ -0,0 +1,52 @@
+package db
+
+import io.getquill.*
+import io.getquill.jdbczio.Quill
+import zio.*
+import javax.sql.DataSource
+
+/** Quill PostgreSQL context with ZIO integration
+  *
+  * Provides compile-time SQL query validation via Quill. Exports two layers:
+  *   - dataSourceLayer: HikariCP-managed connection pool configured from application.conf
+  *   - quillLayer: Quill PostgreSQL context with SnakeCase naming strategy
+  *
+  * Usage:
+  * {{{
+  * import db.QuillContext.*
+  *
+  * def findUser(email: String) =
+  *   run(query[SummerUser].filter(_.email == lift(email)))
+  *     .provide(quillLive)
+  * }}}
+  *
+  * IMPORTANT: Never use "io" as a variable name in files importing Quill
+  * (conflicts with io.getquill package).
+  */
+object QuillContext {
+
+  /** DataSource layer from HikariCP configuration
+    *
+    * Reads configuration from "database" prefix in application.conf.
+    * HikariCP manages the connection pool.
+    */
+  val dataSourceLayer: ZLayer[Any, Throwable, DataSource] =
+    Quill.DataSource.fromPrefix("database")
+
+  /** Quill PostgreSQL context with snake_case naming
+    *
+    * Converts Scala camelCase field names to PostgreSQL snake_case columns.
+    * Example: passwordHash -> password_hash
+    */
+  val quillLayer: ZLayer[DataSource, Nothing, Quill.Postgres[SnakeCase]] =
+    Quill.Postgres.fromNamingStrategy(SnakeCase)
+
+  /** Combined layer for full Quill PostgreSQL access
+    *
+    * Provides both DataSource and Quill context.
+    * Use this when you need to run queries.
+    */
+  val quillLive: ZLayer[Any, Throwable, Quill.Postgres[SnakeCase]] =
+    dataSourceLayer >>> quillLayer
+
+}