Search bar Vim mode

This issue proposes to add Vim mode to flow's search bar. If you are interested in having this feature added, please put a thumbs up.

PR https://github.com/Flow-Launcher/Flow.Launcher/pull/4541:

An opt-in Vim editing mode to the search bar. Toggle it in Settings → General → "Enable Advanced Vim Mode". It is off by default — when disabled, the search bar behaves exactly as before.

### Modes
- **Insert** (default) — normal Flow Launcher behavior
- **Normal** — block caret; keys are interpreted as commands
- **Visual** / **Visual Line** — character-wise / whole-query selection

A small color-coded dot at the left of the box shows the current mode (hidden in Insert).

### Normal mode
- **Motions:** `h l w W b B e E 0 ^ $ %`, `f`/`F`/`t`/`T{char}` with `;`/`,` repeat, and `j`/`k` to move through the results
- **Editing:** `x X s S r{char} ~ dd cc D C Y p`, `gu`/`gU`, undo `u` / redo `Ctrl+R`
- **Operators + text objects:** `d c y gu` combined with `iw`/`aw`, `i"`/`a"`, `i'`/`a'`, `i(`/`a(`, `i[`/`a[`, `i{`/`a{` (e.g. `diw`, `ci"`, `ya(`)
- **Repeat & counts:** `.` repeats the last change; most motions/operators accept a count (`3w`, `5x`, `d3w`, `3f,`)
- **Mode switch:** `i I a A v V`

### Visual mode
Extend the selection with any motion, then operate on it: `x`/`d`, `y`, `c`/`s`, `r{char}`, `~`, `gu`/`gU`. `i`/`a` start a text object, `o` swaps the selection ends, `Esc` returns to Normal.

Review PR #4541 first, then trace Flow Launcher’s search bar and the Settings → General "Enable Advanced Vim Mode" option. Compare the proposed insert, normal, and visual modes with the listed motions and editing commands. Done means the opt-in behavior, mode indicator, and command set work without changing the default search bar behavior.

Written by the indexing model from the issue text.