feat: integrate Tailwind CSS for improved styling and layout

- Added Tailwind CSS and its Vite plugin to the frontend project.
- Updated App.svelte to enhance UI with Tailwind classes, including a new layout for the serial monitor and command tester.
- Improved logging functionality by increasing log history and adding more detailed log messages.
- Refactored SendBox.svelte for consistent styling with Tailwind.
- Enhanced Pico firmware to support structured event logging and command parsing.
- Updated README_PICO_SERIAL.md to provide comprehensive documentation on serial communication and backend integration.
- Added .dockerignore to optimize Docker builds by excluding unnecessary files.

pico/src/main.cpp

@@ -1,50 +1,111 @@
+// Supports two transport modes:
+// 1. USB CDC (Serial) when connected over USB (preferred)
+// 2. Hardware UART0 (Serial1) on GPIO pins for headless Raspberry Pi connection
+//    Wiring for UART mode (3.3V logic only):
+//      Pi GPIO14 (TXD0, physical pin 8)  --> Pico GP1 (UART0 RX)
+//      Pi GPIO15 (RXD0, physical pin 10) <-- Pico GP0 (UART0 TX)
+//      Pi GND (any) <--------------------> Pico GND
+//    Optionally power Pico via USB. If powering from Pi 3V3, DO NOT also power via USB simultaneously.
+
 #include <Arduino.h>
 #include "Stepper.h"
 #include "ULN2003Stepper.h"
 
-
 ULN2003Stepper driver1({18, 19, 20, 21}, 4096);
 int revSteps = 0;
 
+// Generic IO pointers (assigned to USB Serial or Serial1 at runtime)
+Stream* serialIn = nullptr;  // for available()/read()
+Print*  serialOut = nullptr; // for print()/println()
+
 void setup() {
+  // Start USB CDC first
   Serial.begin(115200);
+  unsigned long start = millis();
+  while (!Serial && (millis() - start) < 2000UL) {
+    // wait up to 2 seconds for host to open USB (non-blocking fallback)
+  }
+  if (Serial) {
+    serialIn = &Serial;
+    serialOut = &Serial;
+    Serial.println("INFO: Using USB CDC Serial");
+  } else {
+    // Fall back to UART0 on GPIO0 (TX) / GPIO1 (RX)
+    Serial1.begin(115200); // default pins for UART0 in Arduino-Pico core
+    serialIn = &Serial1;
+    serialOut = &Serial1;
+    Serial1.println("INFO: Using UART0 (Serial1) on GP0(TX)/GP1(RX)");
+  }
   revSteps = driver1.get_steps_per_rev();
-  Serial.print("Steps: ");
-  Serial.println(revSteps);
+  serialOut->print("EVENT:START STEPS_PER_REV ");
+  serialOut->println(revSteps);
+}
+
+// helper: trim leading/trailing whitespace
+static String trim(const String &s) {
+  int start = 0;
+  int end = s.length() - 1;
+  while (start <= end && isspace(s.charAt(start))) start++;
+  while (end >= start && isspace(s.charAt(end))) end--;
+  if (end < start) return String("");
+  return s.substring(start, end + 1);
 }
 
 void loop() {
+  if (!serialIn || !serialOut) return; // safety
   static String input = "";
-  while (Serial.available()) {
-    char c = Serial.read();
+  while (serialIn->available()) {
+    char c = serialIn->read();
     if (c == '\n' || c == '\r') {
-      if (input.length() > 0) {
-        Serial.print("Received: ");
-        Serial.println(input);
+      String cmd = trim(input);
+      if (cmd.length() > 0) {
+        // Emit event: received
+        serialOut->print("EVENT:RECEIVED ");
+        serialOut->println(cmd);
+
+        bool success = true;
+        String result = "OK";
+
         // Parse command
-        if (input.startsWith("STEP ")) {
-          int idx1 = input.indexOf(' ');
-          int idx2 = input.indexOf(' ', idx1 + 1);
-          int steps = input.substring(idx1 + 1, idx2).toInt();
-          int dir = input.substring(idx2 + 1).toInt();
-          driver1.step(steps, dir != 0);
-          Serial.print("Motor moved ");
-          Serial.print(steps);
-          Serial.print(" steps in direction ");
-          Serial.println(dir);
-        } else if (input.startsWith("SPEED ")) {
-          int delay_us = input.substring(6).toInt();
+        if (cmd.startsWith("STEP ")) {
+          int idx1 = cmd.indexOf(' ');
+          int idx2 = cmd.indexOf(' ', idx1 + 1);
+          if (idx1 != -1 && idx2 != -1) {
+            int steps = cmd.substring(idx1 + 1, idx2).toInt();
+            int dir = cmd.substring(idx2 + 1).toInt();
+            // execute
+            driver1.step(steps, dir != 0);
+            // report completion
+            serialOut->print("EVENT:COMPLETED STEP ");
+            serialOut->print(steps);
+            serialOut->print(" ");
+            serialOut->println(dir);
+          } else {
+            success = false;
+            result = "ERROR: malformed STEP command";
+          }
+        } else if (cmd.startsWith("SPEED ")) {
+          int delay_us = cmd.substring(6).toInt();
           driver1.setSpeed(delay_us);
-          Serial.print("Speed set to ");
-          Serial.println(delay_us);
-        } else if (input.startsWith("LOG ")) {
-          Serial.print("LOG: ");
-          Serial.println(input.substring(4));
+          serialOut->print("EVENT:COMPLETED SPEED ");
+          serialOut->println(delay_us);
         } else {
-          Serial.println("Unknown command");
+          success = false;
+          result = "ERROR: unknown command";
+          serialOut->print("EVENT:COMPLETED ");
+          serialOut->println(result);
+        }
+
+        // always print a short status summary
+        if (success) {
+          serialOut->print("STATUS: ");
+          serialOut->println("OK");
+        } else {
+          serialOut->print("STATUS: ");
+          serialOut->println(result);
         }
-        input = "";
       }
+      input = "";
     } else {
       input += c;
     }