fix(arcrun): address PR #2 review findings

Security:
- init.ts: remove cf_api_token from POST /register (only email sent to arcrun.dev)
- cf-api.ts: remove base64 fallback in encryptCredential, throw clear error if key missing

Correctness:
- submitComponent.ts: replace KBDB dependency with SUBMISSIONS_KV + R2 (standalone)
- registry/types.ts: remove KBDB_URL/KBDB_INTERNAL_TOKEN, add SUBMISSIONS_KV/ANALYTICS_KV
- webhooks.ts: add waitUntil(writeExecutionVerdict) for fire-and-forget analytics
- execution-logger.ts: create missing module (was imported but didn't exist)
- cypher-executor/types.ts + wrangler.toml: add ANALYTICS_KV binding
- gmail/telegram/google_sheets/line_notify/http_request: no_network_syscall false (api category)
- init.ts: replace require() with await import() for ES module compatibility

Cleanup:
- Remove arcrun/builtins/ (dead code — initComponents used old HTTP endpoint model,
  all 21 components now in TinyGo WASM under registry/components/)

Docs:
- tasks.md: update to reflect completed work and remaining items

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

cypher-executor/wrangler.toml

@@ -20,6 +20,11 @@ id = ""   # 填入你的 KV Namespace ID
 binding = "CREDENTIALS_KV"
 id = ""   # 填入你的 Credentials KV Namespace ID
 
+# Analytics：執行統計（fire-and-forget，保留 90 天）
+[[kv_namespaces]]
+binding = "ANALYTICS_KV"
+id = ""   # 填入你的 Analytics KV Namespace ID
+
 # R2 Bucket：WASM 零件二進位（arcrun.dev 公眾零件庫，或自架時填入自己的 bucket）
 [[r2_buckets]]
 binding = "WASM_BUCKET"