webui: add file picker

[glowinthedark]

Problem description

The current Web UI requires user to enter the full path to input and output files, basically just pasting it from somewhere, which is clunky and not easy to use.

Solution

A. Provide path auto-suggest when user starts typing in the inputs
B. Add a 📁 Browse button that mimics a desktop-style file picker.

Changes

• add js and ws://listDir hooks for directory/file path autosuggest on user input
• add 📁 browse buttons for ws://listDir
• (cleanup) browse.html: replace hard-coded format list with existing /config endpoint

[glowinthedark]

@ilius: i see there is an error specifically on 3.12, the agent identified it's probably collect-coverage.sh#L4

and can be fixed by changing:

rootDir=$(dirname $(dirname $(realpath $(dirname "$0"))))

to

rootDir=$(git rev-parse --show-toplevel)

no sure if this is the real root cause, and if that needs to be in this pr or not 🤔

Update

not sure if the test failure is intermittent or not but using rootDir=$(git rev-parse --show-toplevel) seems to make the workflow pass successfully; here is the result with a side branch:

https://github.com/glowinthedark/pyglossary/actions/runs/27878724674

please let me know if you want this fixed in this pr - I'm assuming not in this scope, right?

[glowinthedark]

@ilius: another issue gml5.2 pointed out which I suspect has nothing to do with the test failure is that sqlite3.connect("file::memory:") requires uri=True to work as expected since this is URI syntax and python should parse it before handing it over to the C native module, otherwise it's treated as an actual disc file, so should either be sqlite3.connect("file::memory:", uri=True) or simply sqlite3.connect(":memory:")