PlanOpticon

feat(graph): replace FalkorDB with SQLite, add kg CLI utilities - Replace FalkorDBStore with SQLiteStore using Python's built-in sqlite3 - Remove falkordblite/redis dependencies from pyproject.toml - Make SQLite the primary knowledge graph format (.db is default) - Pipeline and orchestrator now build into SQLite, export JSON copy - Batch merge prefers .db files, falls back to .json - KnowledgeGraph.save() defaults to .db extension - Rename cypher() to sql() in query engine and CLI - Add `planopticon kg` CLI group with convert, sync, and inspect commands - Update graph_discovery.py, CLAUDE.md, output_structure.py references - Replace FalkorDB tests with SQLite tests (54 tests, all passing) Closes #54, #55, #56, #57