chore: auto-fix Biome formatting and configure lint rules

Run biome check --write --unsafe to fix tabs, import ordering, and
non-null assertions across entire codebase. Disable a11y rules not
applicable to this single-user app. Exclude auto-generated routeTree.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

drizzle/meta/_journal.json

@@ -1,20 +1,20 @@
 {
-  "version": "7",
-  "dialect": "sqlite",
-  "entries": [
-    {
-      "idx": 0,
-      "version": "6",
-      "when": 1773589489626,
-      "tag": "0000_bitter_luckman",
-      "breakpoints": true
-    },
-    {
-      "idx": 1,
-      "version": "6",
-      "when": 1773593102000,
-      "tag": "0001_rename_emoji_to_icon",
-      "breakpoints": true
-    }
-  ]
+	"version": "7",
+	"dialect": "sqlite",
+	"entries": [
+		{
+			"idx": 0,
+			"version": "6",
+			"when": 1773589489626,
+			"tag": "0000_bitter_luckman",
+			"breakpoints": true
+		},
+		{
+			"idx": 1,
+			"version": "6",
+			"when": 1773593102000,
+			"tag": "0001_rename_emoji_to_icon",
+			"breakpoints": true
+		}
+	]
 }