refactor: migrate observability to fireflyframework-observability

- Add fireflyframework-observability dependency
- Extend FireflyMetricsSupport/FireflyHealthIndicator base classes
- Use centralized metric naming (firefly.{module}.{metric}) and tag constants
- Replace duplicate logback-spring.xml with shared logback-firefly.xml include
- Remove direct micrometer/otel/brave/logstash dependencies

Author: ancongui

pom.xml

@@ -61,46 +61,11 @@
             <artifactId>spring-boot-starter-actuator</artifactId>
         </dependency>
 
-        <!-- Micrometer Tracing for distributed tracing -->
+        <!-- Observability (metrics, tracing, health, structured logging) -->
         <dependency>
-            <groupId>io.micrometer</groupId>
-            <artifactId>micrometer-tracing</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>io.micrometer</groupId>
-            <artifactId>micrometer-tracing-bridge-brave</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>io.zipkin.reporter2</groupId>
-            <artifactId>zipkin-reporter-brave</artifactId>
-        </dependency>
-
-        <!-- OpenTelemetry for advanced tracing -->
-        <dependency>
-            <groupId>io.micrometer</groupId>
-            <artifactId>micrometer-tracing-bridge-otel</artifactId>
-        </dependency>
-        <dependency>
-            <groupId>io.opentelemetry</groupId>
-            <artifactId>opentelemetry-exporter-zipkin</artifactId>
-        </dependency>
-
-        <!-- Micrometer Registry for Prometheus -->
-        <dependency>
-            <groupId>io.micrometer</groupId>
-            <artifactId>micrometer-registry-prometheus</artifactId>
-        </dependency>
-
-        <!-- Logback JSON Encoder -->
-        <dependency>
-            <groupId>net.logstash.logback</groupId>
-            <artifactId>logstash-logback-encoder</artifactId>
-        </dependency>
-        
-        <!-- Janino for logback conditional expressions -->
-        <dependency>
-            <groupId>org.codehaus.janino</groupId>
-            <artifactId>janino</artifactId>
+            <groupId>org.fireflyframework</groupId>
+            <artifactId>fireflyframework-observability</artifactId>
+            <version>${project.version}</version>
         </dependency>
 
         <!-- Lombok for reducing boilerplate code -->