feat(v2): T-309 SQLite fall-event persistence (mattn/go-sqlite3)

Persist confirmed fall events to a local SQLite DB under artifacts/:
camera host/port/channel + event id/track/source/config version/state/
latency/screenshot path/confirmed-at. Schema stores no password (guarded
by test). Wire openRecorder/saveRecord into the alerts loop; failures are
non-fatal. Re-applied the SILVER-POSE vendored os_windows.go patch that
go mod vendor reverted.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

v2/internal/store/store.go

@@ -0,0 +1,93 @@
+// Package store persists confirmed fall events to a local SQLite database.
+// The database is local, untracked evidence: it records the camera host, port
+// and channel but never the password.
+package store
+
+import (
+	"database/sql"
+	"fmt"
+
+	_ "github.com/mattn/go-sqlite3"
+)
+
+// Record is one confirmed fall event row.
+type Record struct {
+	EventID        string
+	TrackID        string
+	SourceID       string
+	CameraHost     string
+	CameraPort     int
+	CameraChannel  string
+	ConfigVersion  string
+	State          string
+	LatencySeconds float64
+	ScreenshotPath string
+	ConfirmedAtUTC string
+}
+
+type Store struct {
+	db *sql.DB
+}
+
+const schema = `
+CREATE TABLE IF NOT EXISTS fall_events (
+	id INTEGER PRIMARY KEY AUTOINCREMENT,
+	event_id TEXT NOT NULL,
+	track_id TEXT,
+	source_id TEXT,
+	camera_host TEXT,
+	camera_port INTEGER,
+	camera_channel TEXT,
+	config_version TEXT,
+	state TEXT,
+	latency_seconds REAL,
+	screenshot_path TEXT,
+	confirmed_at_utc TEXT
+);`
+
+// Open opens (creating if needed) the SQLite database and ensures the schema.
+func Open(path string) (*Store, error) {
+	db, err := sql.Open("sqlite3", path)
+	if err != nil {
+		return nil, fmt.Errorf("open fall database: %w", err)
+	}
+	if _, err := db.Exec(schema); err != nil {
+		_ = db.Close()
+		return nil, fmt.Errorf("create fall table: %w", err)
+	}
+	return &Store{db: db}, nil
+}
+
+// Save inserts one confirmed fall event.
+func (store *Store) Save(record Record) error {
+	_, err := store.db.Exec(
+		`INSERT INTO fall_events
+			(event_id, track_id, source_id, camera_host, camera_port, camera_channel,
+			 config_version, state, latency_seconds, screenshot_path, confirmed_at_utc)
+		 VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?, ?, ?)`,
+		record.EventID, record.TrackID, record.SourceID,
+		record.CameraHost, record.CameraPort, record.CameraChannel,
+		record.ConfigVersion, record.State, record.LatencySeconds,
+		record.ScreenshotPath, record.ConfirmedAtUTC,
+	)
+	if err != nil {
+		return fmt.Errorf("insert fall event: %w", err)
+	}
+	return nil
+}
+
+// Count returns the number of stored events (used by tests).
+func (store *Store) Count() (int, error) {
+	var count int
+	if err := store.db.QueryRow(`SELECT COUNT(*) FROM fall_events`).Scan(&count); err != nil {
+		return 0, err
+	}
+	return count, nil
+}
+
+func (store *Store) Close() error {
+	if store == nil || store.db == nil {
+		return nil
+	}
+	return store.db.Close()
+}