feat: persist configured databases and connect from sidebar

src/main.rs

@@ -13,7 +13,7 @@ Usage:
   dbdash --sqlite PATH
   dbdash --help
 
-Run without a connection argument to open the in-app connection screen:
+Run without a connection argument to open the saved database list:
   cargo run
 Use the in-app password field to keep credentials out of process arguments.
 
@@ -26,23 +26,28 @@ Expansion never runs shell commands. Quote CLI paths to let dbdash expand them.
 PostgreSQL URLs and libpq-style key=value strings are accepted.
 Use sslmode=require for mandatory TLS; certificates and hostnames are verified.
 Use sslmode=disable only for trusted local connections.
-The inspector needs 70×12 terminal cells; the PostgreSQL form needs 70×16.
+The inspector needs 70×12 terminal cells; the PostgreSQL window needs 74×20.
 
 Navigation:
-  Tab / Esc     Switch focus / return to relations
-  Up/Down, j/k  Move selection (Enter opens a relation)
+  Tab/Shift-Tab Cycle focus: databases, relations, rows (Esc returns to databases)
+  Up/Down, j/k  Move selection (Enter connects to a database or opens a relation)
   Home/End, g/G First / last item
   s             Toggle rows and column schema
   Left/Right    Scroll columns (h/l also work)
   n/p, PgDn/Up  Next / previous 100-row page
-  c             Open the connection screen (Esc keeps the current database)
+  c             Add a configured database in a floating window
   r             Refresh relations and the active relation
   q / Ctrl-C    Quit
-  Connection screen: Up/Down chooses a provider; Enter starts editing.
+  New database window: Up/Down chooses a provider; Enter starts editing.
   Tab/Shift-Tab changes fields; Left/Right changes TLS when that field is focused.
-  Enter connects; Esc cancels; Ctrl-U clears a field. Pasting is supported.
-  Form details are session-only. Passwords clear after connecting or cancelling.
+  Enter saves without connecting, including when the database is offline.
+  Select a saved database and press Enter to connect. PostgreSQL prompts for a
+  password; Esc cancels. Passwords are masked, never saved, and clear on success
+  or cancellation. Ctrl-U clears a field; pasting is supported.
   Enter the database user explicitly; the operating-system username is not used.
+  Configurations persist in $XDG_CONFIG_HOME/dbdash/connections.sqlite3, falling
+  back to ~/.config/dbdash/connections.sqlite3. SQLite paths are saved absolute.
+  CLI connections are not saved. Failed switches keep the current database open.
 
 PostgreSQL reads are enforced read-only and have a 5-second query timeout.
 SQLite files are opened read-only, with a 5-second lock wait but no query timeout.