Optimize dependency installation in start scripts to skip if already satisfied

start.bat

@@ -39,18 +39,30 @@ if not exist "%VENV_DIR%\Scripts\python.exe" (
 
 set "VPY=%VENV_DIR%\Scripts\python.exe"
 
-echo [*] Installing dependencies ...
-"%VPY%" -m pip install --disable-pip-version-check -q --upgrade pip >nul
-"%VPY%" -m pip install --disable-pip-version-check -q -r requirements.txt
-if errorlevel 1 (
-    echo [!] PyPI install failed. Retrying via runflare mirror ...
-    "%VPY%" -m pip install --disable-pip-version-check -q -r requirements.txt ^
-        -i https://mirror-pypi.runflare.com/simple/ ^
-        --trusted-host mirror-pypi.runflare.com
+REM -------- Skip dependency install when all required packages are already importable.
+REM Pip install (even with -q) takes ~3-8s every launch; this drops it to ~0.1s
+REM on warm runs.  Falls through to the install path on first run, after a
+REM requirements.txt change, or when any import fails for any reason.
+set "DEPS_OK=0"
+"%VPY%" -c "import cryptography, h2, brotli, zstandard" >nul 2>&1
+if !errorlevel!==0 set "DEPS_OK=1"
+
+if "!DEPS_OK!"=="1" (
+    echo [*] Dependencies already installed — skipping pip install.
+) else (
+    echo [*] Installing dependencies ...
+    "%VPY%" -m pip install --disable-pip-version-check -q --upgrade pip >nul
+    "%VPY%" -m pip install --disable-pip-version-check -q -r requirements.txt
     if errorlevel 1 (
-        echo [X] Could not install dependencies.
-        pause
-        exit /b 1
+        echo [!] PyPI install failed. Retrying via runflare mirror ...
+        "%VPY%" -m pip install --disable-pip-version-check -q -r requirements.txt ^
+            -i https://mirror-pypi.runflare.com/simple/ ^
+            --trusted-host mirror-pypi.runflare.com
+        if errorlevel 1 (
+            echo [X] Could not install dependencies.
+            pause
+            exit /b 1
+        )
     )
 )