refactor: remove memory slot system and Memories section from PrestigeTab

- Remove deepMemory prestige upgrade from constants/prestige.ts
- Remove Memory interface from types.ts
- Remove memorySlots, memories, addMemory, removeMemory, clearMemories from prestigeStore.ts
- Remove deepMemory/memory references from gameLoopActions.ts
- Remove MemoriesCard component and its usage from PrestigeTab.tsx
- Remove memorySlots display from LoopStatsSection.tsx
- Update tests: store-actions-combat-prestige.test.ts, PrestigeTab.test.ts, tick-integration.test.ts

The memory slot system was fully wired but had no gameplay mechanic — addMemory()
was never called outside tests. This removes dead code across 9 files.

src/lib/game/__tests__/tick-integration.test.ts

@@ -64,9 +64,7 @@ function resetAllStores() {
     totalInsight: 0,
     loopInsight: 0,
     prestigeUpgrades: {},
-    memorySlots: 3,
     pactSlots: 1,
-    memories: [],
     defeatedGuardians: [],
     signedPacts: [],
     signedPactDetails: {},