Clean up server architecture for multi-instance deployment

- Remove main_cycling.py, main_multi.py, main_release.py (single main.py is canonical)
- Update setup.sh to read SERVICE_NAME and PORT from .env
- Update env.example with SERVICE_NAME and PORT for multi-instance support
- Fix server-csi to try rpicam-still before libcamera-still (Debian Trixie)

Deploy pattern: clone repo twice, configure each .env, run setup.sh
Each instance gets its own systemd service and install directory.

server-csi/main.py

@@ -142,33 +142,37 @@ class CSICameraManager:
                 return None
 
     def _capture_libcamera(self) -> Optional[bytes]:
-        """Fallback: use libcamera-still command"""
-        try:
-            cmd = [
-                "libcamera-still",
-                "-n",  # No preview
-                "-o", "-",  # Output to stdout
-                "--width", str(self.width),
-                "--height", str(self.height),
-                "-q", str(JPEG_QUALITY),
-                "-t", "1",  # 1ms timeout (immediate capture)
-            ]
-            
-            if self.rotation:
-                cmd.extend(["--rotation", str(self.rotation)])
-            
-            result = subprocess.run(cmd, capture_output=True, timeout=10)
-            if result.returncode == 0:
-                return result.stdout
-            else:
-                print(f"libcamera-still error: {result.stderr.decode()}")
-                return None
-        except subprocess.TimeoutExpired:
-            print("libcamera-still timed out")
-            return None
-        except FileNotFoundError:
-            # Try raspistill (older Pi OS)
-            return self._capture_raspistill()
+        """Fallback: use rpicam-still/libcamera-still command"""
+        # Try rpicam-still first (Debian Trixie / newer Pi OS)
+        for cmd_name in ["rpicam-still", "libcamera-still"]:
+            try:
+                cmd = [
+                    cmd_name,
+                    "-n",  # No preview
+                    "-o", "-",  # Output to stdout
+                    "--width", str(self.width),
+                    "--height", str(self.height),
+                    "-q", str(JPEG_QUALITY),
+                    "-t", "1",  # 1ms timeout (immediate capture)
+                ]
+                
+                if self.rotation:
+                    cmd.extend(["--rotation", str(self.rotation)])
+                
+                result = subprocess.run(cmd, capture_output=True, timeout=10)
+                if result.returncode == 0:
+                    return result.stdout
+                else:
+                    print(f"{cmd_name} error: {result.stderr.decode()}")
+                    continue
+            except subprocess.TimeoutExpired:
+                print(f"{cmd_name} timed out")
+                continue
+            except FileNotFoundError:
+                continue
+        
+        # Fall back to raspistill (older Pi OS)
+        return self._capture_raspistill()
 
     def _capture_raspistill(self) -> Optional[bytes]:
         """Legacy fallback: use raspistill command"""