Returns a JSON array of all configured VLANs with their IDs and names,
e.g. [{"id":1,"name":""},{"id":20,"name":"IoT"}].
The endpoint iterates VLAN IDs 1..4094 and filters by the validity bit
in sfr_data[0] (0x02), following the same pattern as vlan_create() and
vlan_setup() in rtl837x_port.c.
Also adds a small itoa16_html() helper for emitting decimal numbers
up to 4 digits (analogous to the existing 8-bit itoa_html()), used
for VLAN IDs which can reach 4094. Response builder uses the existing
vlan_name() helper for the name lookup, consistent with send_vlan().
Buffer overflow is prevented by breaking out of the iteration loop at
TCP_OUTBUF_SIZE - 60.
This endpoint is the foundation for upcoming UI improvements
(VLAN selector dropdown and overview table).
flash_read_bulk() is kind of a printf function. But did not work as well.
flash_read_bulk() was used in the http generation so this needed to be changed as well.
For the website we decided that we are going to use CSR(Client Side Rendering).
So every HTML and JS files are now static.
Variables are fetched via json calls and output is render on the client side.
Also usefull for the future when we want a REST like API.
execute_config() was also using flash_read_bulk().
This have been replaced with flash_read_bulk() and parsing the flash_buf buffer.