feat: Implement door interaction system and UI improvements

- Add interactive door system with click detection on door meshes
- Create custom DoorModal component replacing browser confirm()
- Implement door opening with texture change to door1_open.png
- Add additive door rendering to preserve opened doors
- Remove exploration button and requestExploration method
- Implement camera orbit controls with smooth animations
- Add active view indicator (yellow highlight) on camera buttons
- Add vertical zoom slider with label
- Fix camera to maintain isometric perspective while rotating
- Integrate all systems into main game loop

src/engine/game/TurnManager.js

@@ -0,0 +1,65 @@
+import { GAME_PHASES, GAME_EVENTS } from './GameConstants.js';
+
+export class TurnManager {
+    constructor() {
+        this.currentTurn = 0;
+        this.currentPhase = GAME_PHASES.SETUP;
+        this.listeners = {}; // Simple event system
+    }
+
+    startGame() {
+        this.currentTurn = 1;
+        this.setPhase(GAME_PHASES.HERO); // Jump straight to Hero phase for now
+        console.log(`--- TURN ${this.currentTurn} START ---`);
+    }
+
+    nextPhase() {
+        // Simple sequential flow for now
+        switch (this.currentPhase) {
+            case GAME_PHASES.POWER:
+                this.setPhase(GAME_PHASES.HERO);
+                break;
+            case GAME_PHASES.HERO:
+                // Usually goes to Exploration if at edge, or Monster if not.
+                // For this dev stage, let's allow manual triggering of Exploration
+                // via UI, so we stay in HERO until confirmed done.
+                this.setPhase(GAME_PHASES.MONSTER);
+                break;
+            case GAME_PHASES.MONSTER:
+                this.endTurn();
+                break;
+            // Exploration is usually triggered as an interrupt, not strictly sequential
+        }
+    }
+
+    setPhase(phase) {
+        if (this.currentPhase !== phase) {
+            console.log(`Phase Switch: ${this.currentPhase} -> ${phase}`);
+            this.currentPhase = phase;
+            this.emit(GAME_EVENTS.PHASE_CHANGED, phase);
+        }
+    }
+
+    triggerExploration() {
+        this.setPhase(GAME_PHASES.EXPLORATION);
+        // Logic to return to HERO phase would handle elsewhere
+    }
+
+    endTurn() {
+        console.log(`--- TURN ${this.currentTurn} END ---`);
+        this.currentTurn++;
+        this.setPhase(GAME_PHASES.POWER);
+    }
+
+    // -- Simple Observer Pattern --
+    on(event, callback) {
+        if (!this.listeners[event]) this.listeners[event] = [];
+        this.listeners[event].push(callback);
+    }
+
+    emit(event, data) {
+        if (this.listeners[event]) {
+            this.listeners[event].forEach(cb => cb(data));
+        }
+    }
+}