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>

.planning/config.json

@@ -1,14 +1,14 @@
 {
-  "mode": "yolo",
-  "granularity": "coarse",
-  "parallelization": true,
-  "commit_docs": true,
-  "model_profile": "quality",
-  "workflow": {
-    "research": false,
-    "plan_check": true,
-    "verifier": true,
-    "nyquist_validation": true,
-    "_auto_chain_active": true
-  }
-}
+	"mode": "yolo",
+	"granularity": "coarse",
+	"parallelization": true,
+	"commit_docs": true,
+	"model_profile": "quality",
+	"workflow": {
+		"research": false,
+		"plan_check": true,
+		"verifier": true,
+		"nyquist_validation": true,
+		"_auto_chain_active": true
+	}
+}