feat(examples): declare library manifests for the two lib-using AVR examples (P2.4-arduino examples)

lcd-hello -> ['LiquidCrystal'], uno-servo -> ['Servo']. These were the only
non-ESP32 gallery examples using a USER library without a manifest; loading +
compiling them now sends the library scope (resolved from the content-addressed
cache) instead of falling back to the global scan-all. Every other non-ESP32
example is core-only (Wire/SPI are core-bundled; the RP2040 core bundles Servo,
so pico-servo needs no manifest) or already declared its libraries.

frontend/src/data/examples.ts

@@ -2725,6 +2725,7 @@ void loop() {
     description: 'Display text on a 20x4 LCD using the LiquidCrystal library',
     category: 'displays',
     difficulty: 'intermediate',
+    libraries: ['LiquidCrystal'],
     code: `// LiquidCrystal Library - Hello World
 // Demonstrates the use a 20x4 LCD display
 
@@ -6491,6 +6492,7 @@ void loop() {
     category: 'robotics',
     difficulty: 'beginner',
     boardFilter: 'arduino-uno',
+    libraries: ['Servo'],
     code: `// Arduino Uno — Servo Motor Sweep
 // Wiring: PWM → pin 9  |  V+ → 5V  |  GND → GND
 // Uses the built-in Servo library (no install needed)