Show trustworthy local-day activity totals (#90)

Add local-day activity summaries derived from UTC hour observations using
the system timezone, with durable storage in a new local_days table.
The collector derives local-day read/write totals after UTC aggregation;
the TUI displays them with timezone, completeness state, and coverage.

Schema: bump SCHEMA_VERSION to 3, add local_days table (migration 2→3
is pure addition, idempotent, preserves newer-schema refusal).

tests/test_collector_tracer.py

@@ -244,10 +244,11 @@ def test_store_initialization(config_fixture: Dict[str, Any]):
         "controller_segments",
         "endurance_baseline",
     }
-    
+
     # sqlite_sequence is a system table created by AUTOINCREMENT
     expected_tables.add("sqlite_sequence")
     expected_tables.add("store_metadata")
+    expected_tables.add("local_days")
     assert expected_tables == tables
     
     conn.close()