feat: automatic releases on merge to main

- Drone now triggers on push to main branch instead of Git tags
- Each merge produces two Docker tags: main-{commit-sha} and main-latest
- No manual Git tags needed — merging PR develop → main is the release
- Updated docs/DEVELOPMENT.md with new Git-flow workflow
- Updated CHANGELOG.md with automatic releases feature

.idea/compiler.xml

@@ -1,5 +1,12 @@
 <?xml version="1.0" encoding="UTF-8"?>
 <project version="4">
+  <component name="CompilerConfiguration">
+    <bytecodeTargetLevel>
+      <module name="backend" target="21" />
+      <module name="backend.main" target="21" />
+      <module name="backend.test" target="21" />
+    </bytecodeTargetLevel>
+  </component>
   <component name="JavacSettings">
     <option name="ADDITIONAL_OPTIONS_OVERRIDE">
       <module name="backend" options="-parameters" />