Initial commit: smartrun MVP

Garmin run classification and progression tracker. Go backend (MCP
client to mcp-garmin, SQLite store, deterministic rule engine, REST
API) and React/TS frontend (Dashboard, Review Queue, Workout Kinds).

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

backend/internal/store/migrations/0002_sync_state.sql

@@ -0,0 +1,11 @@
+-- Tracks how far back a full backfill has already reached. Garmin activity
+-- history is immutable once recorded, so once we've backfilled a historical
+-- window there is no need to ever re-fetch get_activities() for it again --
+-- this is the "cache" that lets repeated backfills be cheap/fast instead of
+-- re-walking years of history against Garmin's API every time.
+CREATE TABLE sync_state (
+    id                   INTEGER PRIMARY KEY CHECK (id = 1),
+    earliest_synced_date TEXT,
+    backfill_complete    INTEGER NOT NULL DEFAULT 0
+);
+INSERT INTO sync_state (id, earliest_synced_date, backfill_complete) VALUES (1, NULL, 0);