fix: reject providers missing adapter type

[EterUltimate]

Fixes #9399.

Evidence

• Issue [Bug] 填写provider配置时，出现状态不一致问题 #9399 includes a dashboard stack trace for POST /api/v1/provider-sources/providers ending in KeyError('type') at astrbot/core/provider/manager.py inside load_provider.
• Current ProviderManager.create_provider appends the new provider to config["provider"], saves config, and only then calls load_provider; a missing merged type therefore both raises and leaves a bad provider persisted.
• The reported path matches the current code path: astrbot/dashboard/api/providers.py -> ProviderConfigService.create_provider -> ProviderManager.create_provider -> load_provider.

Changes

• Validate enabled provider configs after provider-source merge and before create/update saves.
• Skip already-corrupt enabled provider configs missing adapter type during load_provider instead of raising KeyError.
• Move the PersonaManager annotation import behind TYPE_CHECKING to avoid the circular import exposed by the new core regression test.
• Add regression coverage for no-save-on-invalid-provider and no-KeyError loading behavior.

Merge plan

• fix: use current provider selection when regenerating chat message #9402 is the minimal existing fix for [Bug]聊天页面第一次使用配置不完整的供应商，出现invaild key错误 #9400 (ChatUI basic retry provider selection) and already has green checks. Merge fix: use current provider selection when regenerating chat message #9402 for that issue.
• Merge this PR independently for [Bug] 填写provider配置时，出现状态不一致问题 #9399 after review/CI. It intentionally does not duplicate the [Bug]聊天页面第一次使用配置不完整的供应商，出现invaild key错误 #9400 frontend change.

Verification

• uv run ruff check .
• uv run ruff format --check .
• uv run pytest tests/unit/test_provider_manager_config_validation.py tests/test_fastapi_v1_dashboard.py -q -> 74 passed
• uv run pytest tests/unit/test_provider_manager_config_validation.py tests/test_fastapi_v1_dashboard.py::test_v1_safe_provider_routes_accept_slash_ids tests/test_chat_route.py -q -> 12 passed
• uv run astrbot --help
• cd dashboard && bunx pnpm@10.28.2 install --frozen-lockfile
• cd dashboard && bunx pnpm@10.28.2 run build

Full local Windows pytest was also run with uv run pytest --cov=astrbot tests/ -q: 1841 passed, 28 failed. The failures are existing Windows path/newline/sandbox/file-uri/local-shell cases outside the provider files touched here; targeted provider/API tests passed. tests/test_code_quality_typing.py is not present on current origin/master, so it could not be run.

• This is NOT a breaking change. / 这不是一个破坏性变更。
• I have ensured that no new dependencies are introduced.
• My changes do not introduce malicious code.

Summary by Sourcery

Validate provider configurations for a valid adapter type before persisting them and ensure loading skips invalid providers instead of raising errors.

Bug Fixes:

• Prevent saving new or updated providers whose merged configuration is missing a valid adapter type field.
• Avoid KeyError and other crashes when loading enabled providers that lack a valid adapter type by skipping them instead.

Enhancements:

• Guard provider creation and update with a centralized provider config validation helper.
• Adjust PersonaManager typing to avoid circular import issues exposed by tests.

Tests:

• Add unit tests covering rejection of invalid provider configs before save and safe skipping of missing-type providers during load.