feat: Add pause/resume functionality to time tracking

Add pausedAt and pausedDuration columns to time_entries table.
New pause/resume endpoints with audit logging. Duration calculations
now correctly exclude paused time across start, stop, auto-stop,
and edit flows.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/db/migrations/0010_add_timer_pause.sql

@@ -0,0 +1,2 @@
+ALTER TABLE "time_entries" ADD COLUMN IF NOT EXISTS "paused_at" timestamp;
+ALTER TABLE "time_entries" ADD COLUMN IF NOT EXISTS "paused_duration" integer NOT NULL DEFAULT 0;

src/db/schema.js

@@ -282,6 +282,8 @@ export const timeEntries = pgTable('time_entries', {
   description: text('description'), // popis práce
   isRunning: boolean('is_running').default(false).notNull(), // či práve beží
   isEdited: boolean('is_edited').default(false).notNull(), // či bol editovaný
+  pausedAt: timestamp('paused_at'), // kedy bola aktuálna pauza spustená (null ak nepauznutý)
+  pausedDuration: integer('paused_duration').default(0).notNull(), // celkový čas pauzy v sekundách
   createdAt: timestamp('created_at').defaultNow().notNull(),
   updatedAt: timestamp('updated_at').defaultNow().notNull(),
 });