Apply UI improvements from CAN branch to uart-backend

[Copilot]

The copilot/add-support-list-device-error-logs CAN branch introduced several UI/UX improvements that were not reflected in the uart-backend. This ports all applicable changes, skipping CAN-specific features (node ID, CAN pin settings).

data/inverter.js

• Move communication error bar logic from getParamList into sendCmd via onreadystatechange — now tracks HTTP status directly rather than JSON parse failures
• Remove firmwareVersion < 3.53 fallback in getValues; always use stream command
• Add console.error on param parse failure instead of silent catch

data/ui.js

• Replace showParamUpdateModal (async modal) with sendParameterUpdate — shows a non-blocking green success bar instead
• Dynamic step size for numeric param inputs: 1 for integers, 0.04 for fractional values
• Pause auto-refresh while a param field has focus; resume on blur
• refreshStatusBox no longer returns early on null — each field is individually null-guarded
• File upload success uses showParamSuccessBar instead of modal
• populateSpotValueDropDown moved into updateTables callback (populates from fresh data); clears options before repopulating to prevent duplicates on refresh
• Navbar collapses to 60px (was 80px); navbarIsBig state property added
• Auto-refresh interval: 3000ms → 2000ms

data/index.html

• Add #param-success-bar div for non-blocking param update notifications
• CAN modal: rename "Offset" → "Position"; add canoffset input row (-128–127)
• CAN mapping table: headers updated to match — "Position", "Gain", "Offset"
• Navbar: auto-reload toggle moved before spinner; beta features toggle removed
• Fix "ESP8266" → "ESP32" in support page copy

data/style.css

• Add .param-success-bar styles (green, auto-hidden, centered)

esp32-web-interface.ino

• Add Cache-Control: max-age=86400 for SPIFFS static file responses
• strnlen("binarylogging 0", ...) → strlen(...) (literal, no bound needed)
• Remove server.client().setNoDelay(1) after server.begin()
• Drop unused size_t sent variables