add gitignore and commit Obsidian vault config

Exclude .env (a GOOGLE_CLOUD_PROJECT value was present at the repo root),
.claude/settings.local.json, OS cruft, and personal Obsidian workspace
state (workspace.json, workspace-mobile.json, cache). Commit the rest of
.obsidian/ so the vault reopens with the same plugins, graph settings,
and daily-notes config on any machine.

Also expand Obsidian's userIgnoreFilters so .claude, .env, and .gitignore
don't pollute the file explorer, search, or graph view.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

.obsidian/graph.json

@@ -0,0 +1,22 @@
+{
+  "collapse-filter": true,
+  "search": "",
+  "showTags": false,
+  "showAttachments": false,
+  "hideUnresolved": false,
+  "showOrphans": true,
+  "collapse-color-groups": true,
+  "colorGroups": [],
+  "collapse-display": true,
+  "showArrow": false,
+  "textFadeMultiplier": 0,
+  "nodeSizeMultiplier": 1,
+  "lineSizeMultiplier": 1,
+  "collapse-forces": true,
+  "centerStrength": 0.518713248970312,
+  "repelStrength": 10,
+  "linkStrength": 1,
+  "linkDistance": 250,
+  "scale": 1,
+  "close": false
+}