chore: bump version to 0.7.12 across the app + docs/website

Sync version in desktop/package.json, Cargo.toml, tauri.conf.json, the Astro
landing page, version/bundle-config/docs-coverage tests, and both README
download tables. Add v0.7.12 changelog entry.

desktop/src-tauri/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "gridline"
-version = "0.7.11"
+version = "0.7.12"
 description = "An open-source, high-performance database GUI client for PostgreSQL and beyond"
 authors = ["you"]
 edition = "2021"

desktop/src-tauri/tauri.conf.json

@@ -1,7 +1,7 @@
 {
   "$schema": "https://schema.tauri.app/config/2",
   "productName": "Gridline",
-  "version": "0.7.11",
+  "version": "0.7.12",
   "identifier": "com.adrianbonpin.gridline",
   "build": {
     "beforeDevCommand": "bun run dev",