Update Docker image name to windwatts-api for consistency

[Copilot]

Addresses feedback from #176 to align Docker image naming with the WindWatts project name.

Changes

• Updated all Docker commands in docs/06-deployment.md to use windwatts-api instead of tap-api
  • Build command
  • Production run command
  • Troubleshooting command

# Before
docker build -t tap-api:latest .
docker run -p 8080:80 -it tap-api:latest uvicorn app.main:app --host 0.0.0.0 --port 80 --workers 4

# After
docker build -t windwatts-api:latest .
docker run -p 8080:80 -it windwatts-api:latest uvicorn app.main:app --host 0.0.0.0 --port 80 --workers 4

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