docs: fix inaccuracies, add translations, and expand channel docs (#1837)

## Config field fixes (cross-verified against Go source)
- MaixCam: server_address → host + port
- IRC: use_tls → tls, channels_to_join → channels (all 6 languages)
- WeCom AI Bot: callback port 18791 → 18790
- credential_encryption: base_url → api_base, add required model field,
  remove incorrect passphrase-only mode docs
- providers.md: agents.defaults.model → model_name (×4), remove
  non-existent session.backlog_limit
- migration guide, troubleshooting: agents.defaults.model → model_name
- ANTIGRAVITY_AUTH: fix file path, Go 1.21 → 1.25, model → model_name
- spawn-tasks: fix truncated file, add Heartbeat introduction
- tools_configuration: add Tavily/SearXNG/GLMSearch, exec allow_remote/
  timeout_seconds/custom_allow_patterns, cron allow_command, skills
  github/search_cache, clawhub timeout/max_zip_size/max_response_size
- configuration: fix builtin skills path (build-time embedded, not cwd),
  HEARTBEAT.md marked auto-generated

## Broken link fixes (15 total)
- chat-apps.md: WeCom/Matrix links with wrong relative paths
- providers.md: migration link with extra docs/ prefix
- hardware-compatibility.md: README links with wrong depth (all 5 langs)
- chat-apps.md: WhatsApp dead links → anchor links (zh/ja)

## Getting-started accuracy
- README (all 6 langs): add picoclaw.io as recommended download,
  add missing picoclaw model CLI command
- docker.md: clarify first-run trigger condition (all 6 langs)
- configuration.md: fix builtin skills path description (all 6 langs)

## QQ channel
- Add quick setup via q.qq.com/qqbot/openclaw (one-click bot creation)
- Add manual setup as fallback (all 6 languages)

## Feishu channel
- Update setup flow: WebSocket/SDK mode, no webhook URL needed
- Preserve Lark international domain note (all 6 languages)

## chat-apps.md
- Add Feishu, Slack, IRC, OneBot detail sections (all 6 languages)
- Add MaixCam section to ja/fr/pt-br/vi
- Fix all channel doc links to point to correct language version

## New translations (25 files, 5 docs × 5 languages)
debug.md, credential_encryption.md, hardware-compatibility.md,
ANTIGRAVITY_AUTH.md, ANTIGRAVITY_USAGE.md → zh/ja/fr/pt-br/vi

## Channel docs (6 languages each, 60 new files)
telegram, discord, qq, feishu, maixcam, dingtalk, line, slack, onebot,
wecom/wecom_aibot, wecom/wecom_app, wecom/wecom_bot

Co-authored-by: BeaconCat <BeaconCat@users.noreply.github.com>

docs/providers.md

@@ -95,7 +95,7 @@ This design also enables **multi-agent support** with flexible provider selectio
   ],
   "agents": {
     "defaults": {
-      "model": "gpt-5.4"
+      "model_name": "gpt-5.4"
     }
   }
 }
@@ -268,13 +268,13 @@ The old `providers` configuration is **deprecated** but still supported for back
   ],
   "agents": {
     "defaults": {
-      "model": "glm-4.7"
+      "model_name": "glm-4.7"
     }
   }
 }
 ```
 
-For detailed migration guide, see [docs/migration/model-list-migration.md](docs/migration/model-list-migration.md).
+For detailed migration guide, see [migration/model-list-migration.md](migration/model-list-migration.md).
 
 ### Provider Architecture
 
@@ -300,7 +300,7 @@ This keeps the runtime lightweight while making new OpenAI-compatible backends m
   "agents": {
     "defaults": {
       "workspace": "~/.picoclaw/workspace",
-      "model": "glm-4.7",
+      "model_name": "glm-4.7",
       "max_tokens": 8192,
       "temperature": 0.7,
       "max_tool_iterations": 20
@@ -330,12 +330,11 @@ picoclaw agent -m "Hello"
 {
   "agents": {
     "defaults": {
-      "model": "anthropic/claude-opus-4-5"
+      "model_name": "anthropic/claude-opus-4-5"
     }
   },
   "session": {
-    "dm_scope": "per-channel-peer",
-    "backlog_limit": 20
+    "dm_scope": "per-channel-peer"
   },
   "providers": {
     "openrouter": {