chore: add gitignore and drop regenerated fp-info-cache

Ignore KiCad lock files, the regenerated fp-info-cache, Python bytecode,
and editor/tooling local state (.history, .omc). Delete the previously
tracked fp-info-cache since KiCad regenerates it from the active library
tables on demand.

Confidence: high
Scope-risk: narrow

.gitignore

@@ -0,0 +1,13 @@
+# KiCad lock files (created while project is open)
+~*.lck
+
+# KiCad regenerated footprint info cache
+fp-info-cache
+
+# Python bytecode cache
+__pycache__/
+*.pyc
+
+# Editor/tooling local state
+.history/
+.omc/