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>

internal/ui/app/route.go

@@ -5,13 +5,14 @@ import (
 	"fmt"
 	"slices"
 
+	"git.kebcloud.no/keb/lazysecrets/internal/cachefile"
 	"git.kebcloud.no/keb/lazysecrets/internal/provider"
 )
 
 // containerKey identifies a container in the UI and caches. The same vault
 // seen through two accounts must not share cached lists, since each
 // account may see different things.
-func containerKey(c provider.Container) string { return c.Source.Provider + "|" + c.ID }
+func containerKey(c provider.Container) string { return cachefile.ContainerKey(c) }
 
 // providerFor finds the provider instance a source came from. Sources
 // remembered from an earlier run (favourites) may name an account that