feat: lazysecrets list prints everything lazysecrets can find, for fzf and editor pickers (#70)

`lazysecrets list` prints every source, vault and secret lazysecrets can find, one per line, for fzf, editor pickers and scripts: what Go to searches, without the TUI. What's cached prints at once; what's missing or older than `--max-age` loads in the background and streams in. It stops when the reader goes (a pick in fzf), saving what it loaded.

- Text: kind, mark (✗/⚠, ★, ◷ and the provider icon), name, status (why it couldn't be read, or expired / expires in 12d), note, account and link, tab-separated; kind first and account and link last, so new fields go between. Coloured from the theme; `--color never`, `--icons=false`, `--stars=false`, `--recent`, `--notes=false`, `--expiry=false`.
- `--format json`: an object per line, with starred, recent, lastUsed and uses, expires, enabled, note, reference and url too.
- `--kind` lists only some kinds, and doesn't load lists only other kinds need; `--cached` loads nothing.
- `lazysecrets open --action go|copy|show` skips the "what to do" menu and ends in the list, like Go to; `open` and `get` take `--account`, the account list printed, rather than asking which.
- The cache file moved to `internal/cachefile`: saves merge with the file under a lock, so list and the TUI don't undo each other.
- `ui.recentIcon` marks items used lately with ◷ in the TUI's lists too; Recent now means the last 90 days.
- --demo has stars, notes, recent use, and expired, expiring and disabled secrets.
- docs/integration.md documents get, list and an fzf picker; docs/links.md is docs/sharing.md.

Reviewed-on: #70
Co-authored-by: Karl-Einar Bergstrøm <karl-einarb@outlook.com>

docs/repos.md

@@ -58,7 +58,7 @@ providers:
 ```
 
 A repo's `.lazysecrets.yaml` can also name the secret its env files are
-[shared](links.md#sharing-env-files) with:
+[shared](sharing.md#sharing-env-files) with:
 
 ```yaml
 sharing:
@@ -100,7 +100,7 @@ sops 3.8 or later.
 
 ## Links
 
-`S` → `f` shares env files as an [encrypted link](links.md#sharing-env-files).
+`S` → `f` shares env files as an [encrypted link](sharing.md#sharing-env-files).
 
 Links name the repo by its git remote, so they open in a colleague's clone
 wherever it is:
@@ -109,4 +109,4 @@ wherever it is:
 lazysecrets://repo/git.example.com%2Fteam%2Finfra/secrets%2Fapp.yaml/db.password
 ```
 
-See [links](links.md).
+See [sharing](sharing.md).