feat(TRUEREF-0018): implement embedding provider configuration UI

- Full settings page replacing placeholder with embedding provider selector
- Provider presets: OpenAI, Ollama, Azure OpenAI
- Test Connection button via POST /api/v1/settings/embedding/test
- Warning banner for FTS5-only mode when provider=none
- Local model availability probe (@xenova/transformers)

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/settings.local.json

@@ -6,8 +6,17 @@
       "WebFetch(domain:github.com)",
       "Bash(git init:*)",
       "Bash(git add:*)",
-      "Bash(git commit:*)"
-    ]
+      "Bash(git commit:*)",
+      "Bash(git checkout:*)",
+      "Bash(DATABASE_URL=./local.db npx drizzle-kit generate 2>&1)",
+      "Bash(DATABASE_URL=./local.db npx drizzle-kit generate)",
+      "Bash(npm run:*)",
+      "Bash(npm test:*)",
+      "Skill(update-config)",
+      "Bash(git -C /home/moze/Sources/trueref checkout -b feat/TRUEREF-0002-through-0018)",
+      "Bash(git:*)"
+    ],
+    "defaultMode": "bypassPermissions"
   },
   "enableAllProjectMcpServers": true,
   "enabledMcpjsonServers": [