refactor: implement Builder Pattern for DockerComposeContext

- Introduce DockerComposeContextBuilder for flexible, scalable configuration
- Replace specialized constructors (new_sqlite, new_mysql) with unified builder() entry point
- Default to SQLite database configuration (zero-config common case)
- Explicit database override via with_mysql() method
- Consistent optional feature pattern: all use with_* methods
- Move Prometheus configuration to builder chain
- Update all test code and production code to use new builder API

BREAKING CHANGES:
- Removed: DockerComposeContext::new_sqlite(ports)
- Removed: DockerComposeContext::new_mysql(root_password, database, user, password, port, ports)
- Removed: context.with_prometheus(config) post-construction method
- New API: DockerComposeContext::builder(ports).build()
- MySQL: builder(ports).with_mysql(...).build()
- Prometheus: builder(ports).with_prometheus(config).build()

Rationale:
Previous constructor-based API was "chaotic" with:
- Two specialized constructors forcing early database choice
- One mutable method (with_prometheus) inconsistent with immutable constructors
- Poor scalability: future features (Grafana, Redis) would explode constructor count
- Confusing API: when to use constructors vs methods?

Builder pattern provides:
- Single entry point scales infinitely
- SQLite default handles common case with zero config
- Explicit database choice via with_mysql()
- All optional features via consistent with_* pattern
- Clean immutable result after build()
- Self-documenting API (builder chain reads like English)
- Future-proof: easy to add with_grafana(), with_redis(), etc.

This is a complete refactoring with no backward compatibility, justified by:
- Project in early development phase
- Not used in production by end users yet
- Clean migration without technical debt from deprecated APIs
- Better developer experience for future contributors

Author: josecelano

src/application/steps/rendering/docker_compose_templates.rs

@@ -152,10 +152,19 @@ impl<S> RenderDockerComposeTemplatesStep<S> {
 
         // Create contexts based on database configuration
         let database_config = &self.environment.context().user_inputs.tracker.core.database;
-        let (env_context, mut docker_compose_context) = match database_config {
+        let (env_context, docker_compose_context) = match database_config {
             DatabaseConfig::Sqlite { .. } => {
                 let env_context = EnvContext::new(admin_token);
-                let docker_compose_context = DockerComposeContext::new_sqlite(ports);
+
+                let mut builder = DockerComposeContext::builder(ports);
+
+                // Add Prometheus configuration if present
+                if let Some(prometheus_config) = &self.environment.context().user_inputs.prometheus
+                {
+                    builder = builder.with_prometheus(prometheus_config.clone());
+                }
+
+                let docker_compose_context = builder.build();
                 (env_context, docker_compose_context)
             }
             DatabaseConfig::Mysql {
@@ -176,25 +185,26 @@ impl<S> RenderDockerComposeTemplatesStep<S> {
                     password.clone(),
                 );
 
-                let docker_compose_context = DockerComposeContext::new_mysql(
+                let mut builder = DockerComposeContext::builder(ports).with_mysql(
                     root_password,
                     database_name.clone(),
                     username.clone(),
                     password.clone(),
                     *port,
-                    ports,
                 );
 
+                // Add Prometheus configuration if present
+                if let Some(prometheus_config) = &self.environment.context().user_inputs.prometheus
+                {
+                    builder = builder.with_prometheus(prometheus_config.clone());
+                }
+
+                let docker_compose_context = builder.build();
+
                 (env_context, docker_compose_context)
             }
         };
 
-        // Add Prometheus configuration if present
-        if let Some(prometheus_config) = &self.environment.context().user_inputs.prometheus {
-            docker_compose_context =
-                docker_compose_context.with_prometheus(prometheus_config.clone());
-        }
-
         let compose_build_dir = generator
             .render(&env_context, &docker_compose_context)
             .await?;

src/infrastructure/templating/docker_compose/template/renderer/docker_compose.rs

@@ -219,14 +219,15 @@ mod tests {
             http_tracker_ports: vec![7070],
             http_api_port: 1212,
         };
-        let mysql_context = DockerComposeContext::new_mysql(
-            "rootpass123".to_string(),
-            "tracker_db".to_string(),
-            "tracker_user".to_string(),
-            "userpass123".to_string(),
-            3306,
-            ports,
-        );
+        let mysql_context = DockerComposeContext::builder(ports)
+            .with_mysql(
+                "rootpass123".to_string(),
+                "tracker_db".to_string(),
+                "tracker_user".to_string(),
+                "userpass123".to_string(),
+                3306,
+            )
+            .build();
 
         let renderer = DockerComposeRenderer::new(template_manager);
         let output_dir = TempDir::new().unwrap();
@@ -307,7 +308,7 @@ mod tests {
             http_tracker_ports: vec![7070],
             http_api_port: 1212,
         };
-        let sqlite_context = DockerComposeContext::new_sqlite(ports);
+        let sqlite_context = DockerComposeContext::builder(ports).build();
 
         let renderer = DockerComposeRenderer::new(template_manager);
         let output_dir = TempDir::new().unwrap();
@@ -353,7 +354,9 @@ mod tests {
         let prometheus_config = PrometheusConfig {
             scrape_interval: 15,
         };
-        let context = DockerComposeContext::new_sqlite(ports).with_prometheus(prometheus_config);
+        let context = DockerComposeContext::builder(ports)
+            .with_prometheus(prometheus_config)
+            .build();
 
         let renderer = DockerComposeRenderer::new(template_manager);
         let output_dir = TempDir::new().unwrap();
@@ -421,7 +424,7 @@ mod tests {
             http_tracker_ports: vec![7070],
             http_api_port: 1212,
         };
-        let context = DockerComposeContext::new_sqlite(ports);
+        let context = DockerComposeContext::builder(ports).build();
 
         let renderer = DockerComposeRenderer::new(template_manager);
         let output_dir = TempDir::new().unwrap();

src/infrastructure/templating/docker_compose/template/renderer/project_generator.rs

@@ -212,7 +212,7 @@ mod tests {
             http_tracker_ports: vec![7070],
             http_api_port: 1212,
         };
-        DockerComposeContext::new_sqlite(ports)
+        DockerComposeContext::builder(ports).build()
     }
 
     #[tokio::test]