Add battery dispatch implementation and Gitea CI pipeline

Implements the package from PLAN.md: config/data loading, the LP-first
MILP-fallback rolling-horizon optimiser, battery degradation tracking,
independent schedule validation, metrics, plots and the CLI, plus the
matching test suite. Adds a Gitea Actions workflow (lint + tests) that
posts a pass/fail notification to ntfy on every run, and a .gitignore
for build/cache artefacts that had been tracked by mistake.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

.gitignore

@@ -0,0 +1,9 @@
+__pycache__/
+*.pyc
+.venv/
+.ruff_cache/
+.pytest_cache/
+*.egg-info/
+.idea/
+.air/
+.junie/