feat: add PostgreSQL connection form

src/main.rs

@@ -13,7 +13,8 @@ Usage:
   dbdash --sqlite PATH
   dbdash --help
 
-With no argument or DATABASE_URL, the in-app connection screen opens.
+Run without a connection argument and without DATABASE_URL to connect in-app.
+Otherwise DATABASE_URL supplies the PostgreSQL connection when no argument is given.
 Prefer the environment variable to keep passwords out of process arguments:
   export DATABASE_URL='postgresql://user@localhost:5432/database'
   cargo run
@@ -25,7 +26,7 @@ SQLite paths can be relative or absolute; quote paths containing spaces.
 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 terminal must be at least 70 columns wide and 12 lines high.
+The inspector needs 70×12 terminal cells; the PostgreSQL form needs 70×16.
 
 Navigation:
   Tab / Esc     Switch focus / return to relations
@@ -37,6 +38,10 @@ Navigation:
   c             Open the connection screen (Esc keeps the current database)
   r             Refresh relations and the active relation
   q / Ctrl-C    Quit
+  Connection screen: 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.
 
 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.