refactor: Unify leggen and leggend packages into single leggen package

- Merge leggend API components into leggen (api/, services/, background/)
- Replace leggend command with 'leggen server' subcommand
- Consolidate configuration systems into leggen.utils.config
- Update environment variables: LEGGEND_API_URL -> LEGGEN_API_URL
- Rename LeggendAPIClient -> LeggenAPIClient
- Update all documentation, Docker configs, and compose files
- Fix all import statements and test references
- Remove duplicate utility files and clean up package structure

All tests passing (101/101), linting clean, server functionality preserved.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <noreply@anthropic.com>

pyproject.toml

@@ -41,7 +41,6 @@ Repository = "https://github.com/elisiariocouto/leggen"
 
 [project.scripts]
 leggen = "leggen.main:cli"
-leggend = "leggend.main:main"
 
 [dependency-groups]
 dev = [
@@ -58,10 +57,10 @@ dev = [
 ]
 
 [tool.hatch.build.targets.sdist]
-include = ["leggen", "leggend"]
+include = ["leggen"]
 
 [tool.hatch.build.targets.wheel]
-include = ["leggen", "leggend"]
+include = ["leggen"]
 
 [build-system]
 requires = ["hatchling"]