feat: git push status indicator + multi-select bulk push

- DB migration v2: git_pushed_at column on incidents
- markIncidentPushed(id): stamps the push timestamp
- loadGitConfig(): shared helper in lib/git.ts, removes duplication
- Home screen: colored dot per incident (red=never pushed,
  orange=dirty/modified after push, green=up to date);
  dot visible only when git is configured
- Home screen: long-press enters selection mode, tap toggles;
  action bar with Select unpushed / Select all shortcuts +
  bulk push with sequential progress counter
- [id].tsx: marks incident pushed after successful push,
  updates local state without reload

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lib/db.ts

@@ -45,6 +45,13 @@ async function migrate(db: SQLite.SQLiteDatabase): Promise<void> {
       INSERT INTO schema_version (version) VALUES (1);
     `);
   }
+
+  if (current < 2) {
+    await db.execAsync(`
+      ALTER TABLE incidents ADD COLUMN git_pushed_at TEXT;
+      INSERT INTO schema_version (version) VALUES (2);
+    `);
+  }
 }
 
 // --- row mapper ---
@@ -60,6 +67,7 @@ interface IncidentRow {
   created_at: string;
   updated_at: string;
   tags: string;
+  git_pushed_at: string | null;
 }
 
 function rowToIncident(row: IncidentRow): Incident {
@@ -74,6 +82,7 @@ function rowToIncident(row: IncidentRow): Incident {
     createdAt: row.created_at,
     updatedAt: row.updated_at,
     tags: JSON.parse(row.tags) as string[],
+    gitPushedAt: row.git_pushed_at ?? null,
   };
 }
 
@@ -107,6 +116,7 @@ export async function createIncident(draft: IncidentDraft): Promise<Incident> {
     id,
     createdAt: now,
     updatedAt: now,
+    gitPushedAt: null,
   };
 }
 
@@ -163,6 +173,14 @@ export async function deleteIncident(id: string): Promise<void> {
   await db.runAsync("DELETE FROM incidents WHERE id = ?", [id]);
 }
 
+export async function markIncidentPushed(id: string): Promise<void> {
+  const db = await getDb();
+  await db.runAsync(
+    "UPDATE incidents SET git_pushed_at = ? WHERE id = ?",
+    [new Date().toISOString(), id]
+  );
+}
+
 export async function getMaxTitleNumber(prefix: string): Promise<number> {
   const db = await getDb();
   const rows = await db.getAllAsync<{ title: string }>(