refactor: provider & models (#277)

* refactor: move client_type to provider, replace model fields with config JSONB

- Move `client_type` from `models` to `llm_providers` table
- Add `icon` field to `llm_providers`
- Replace `dimensions`, `input_modalities`, `supports_reasoning` on `models`
  with a single `config` JSONB column containing `dimensions`,
  `compatibilities` (vision, tool-call, image-output, reasoning),
  and `context_window`
- Auto-imported models default to vision + tool-call + reasoning
- Update all backend consumers (agent, flow resolver, handlers, memory)
- Regenerate sqlc, swagger, and TypeScript SDK
- Update frontend forms, display, and i18n for new schema

* ui: show provider icon avatar in sidebar and detail header, remove icon input

* feat: add built-in provider registry with YAML definitions and enable toggle

- Add `enable` column to llm_providers (default true, backward-compatible)
- Create internal/registry package to load YAML provider/model definitions
  on startup and upsert into database (new providers disabled by default)
- Add conf/providers/ with OpenAI, Anthropic, Google YAML definitions
- Add RegistryConfig to TOML config (providers_dir, default conf/providers)
- Model listing APIs and conversation flow now filter by enabled providers
- Frontend: enable switch in provider form, green status dot in sidebar,
  enabled providers sorted to top

* fix: make 0041 migration idempotent for fresh databases

Guard data migration steps with column-existence checks so the
migration succeeds on databases created from the updated init schema.

db/queries/models.sql

@@ -1,9 +1,12 @@
 -- name: CreateLlmProvider :one
-INSERT INTO llm_providers (name, base_url, api_key, metadata)
+INSERT INTO llm_providers (name, base_url, api_key, client_type, icon, enable, metadata)
 VALUES (
   sqlc.arg(name),
   sqlc.arg(base_url),
   sqlc.arg(api_key),
+  sqlc.arg(client_type),
+  sqlc.arg(icon),
+  sqlc.arg(enable),
   sqlc.arg(metadata)
 )
 RETURNING *;
@@ -24,6 +27,9 @@ SET
   name = sqlc.arg(name),
   base_url = sqlc.arg(base_url),
   api_key = sqlc.arg(api_key),
+  client_type = sqlc.arg(client_type),
+  icon = sqlc.arg(icon),
+  enable = sqlc.arg(enable),
   metadata = sqlc.arg(metadata),
   updated_at = now()
 WHERE id = sqlc.arg(id)
@@ -36,16 +42,13 @@ DELETE FROM llm_providers WHERE id = sqlc.arg(id);
 SELECT COUNT(*) FROM llm_providers;
 
 -- name: CreateModel :one
-INSERT INTO models (model_id, name, llm_provider_id, client_type, dimensions, input_modalities, supports_reasoning, type)
+INSERT INTO models (model_id, name, llm_provider_id, type, config)
 VALUES (
   sqlc.arg(model_id),
   sqlc.arg(name),
   sqlc.arg(llm_provider_id),
-  sqlc.narg(client_type),
-  sqlc.arg(dimensions),
-  sqlc.arg(input_modalities),
-  sqlc.arg(supports_reasoning),
-  sqlc.arg(type)
+  sqlc.arg(type),
+  sqlc.arg(config)
 )
 RETURNING *;
 
@@ -69,11 +72,6 @@ SELECT * FROM models
 WHERE type = sqlc.arg(type)
 ORDER BY created_at DESC;
 
--- name: ListModelsByClientType :many
-SELECT * FROM models
-WHERE client_type = sqlc.arg(client_type)
-ORDER BY created_at DESC;
-
 -- name: ListModelsByProviderID :many
 SELECT * FROM models
 WHERE llm_provider_id = sqlc.arg(llm_provider_id)
@@ -85,36 +83,25 @@ WHERE llm_provider_id = sqlc.arg(llm_provider_id)
   AND type = sqlc.arg(type)
 ORDER BY created_at DESC;
 
+-- name: ListModelsByProviderClientType :many
+SELECT m.*
+FROM models m
+JOIN llm_providers p ON m.llm_provider_id = p.id
+WHERE p.client_type = sqlc.arg(client_type)
+ORDER BY m.created_at DESC;
+
 -- name: UpdateModel :one
 UPDATE models
 SET
   model_id = sqlc.arg(model_id),
   name = sqlc.arg(name),
   llm_provider_id = sqlc.arg(llm_provider_id),
-  client_type = sqlc.narg(client_type),
-  dimensions = sqlc.arg(dimensions),
-  input_modalities = sqlc.arg(input_modalities),
-  supports_reasoning = sqlc.arg(supports_reasoning),
   type = sqlc.arg(type),
+  config = sqlc.arg(config),
   updated_at = now()
 WHERE id = sqlc.arg(id)
 RETURNING *;
 
--- name: UpdateModelByModelID :one
-UPDATE models
-SET
-  model_id = sqlc.arg(new_model_id),
-  name = sqlc.arg(name),
-  llm_provider_id = sqlc.arg(llm_provider_id),
-  client_type = sqlc.narg(client_type),
-  dimensions = sqlc.arg(dimensions),
-  input_modalities = sqlc.arg(input_modalities),
-  supports_reasoning = sqlc.arg(supports_reasoning),
-  type = sqlc.arg(type),
-  updated_at = now()
-WHERE model_id = sqlc.arg(model_id)
-RETURNING *;
-
 -- name: DeleteModel :exec
 DELETE FROM models WHERE id = sqlc.arg(id);
 
@@ -128,6 +115,48 @@ SELECT COUNT(*) FROM models;
 SELECT COUNT(*) FROM models WHERE type = sqlc.arg(type);
 
 
+-- name: UpsertRegistryProvider :one
+INSERT INTO llm_providers (name, base_url, api_key, client_type, icon, enable, metadata)
+VALUES (sqlc.arg(name), sqlc.arg(base_url), '', sqlc.arg(client_type), sqlc.arg(icon), false, '{}')
+ON CONFLICT (name) DO UPDATE SET
+  icon = EXCLUDED.icon,
+  client_type = EXCLUDED.client_type,
+  updated_at = now()
+RETURNING *;
+
+-- name: UpsertRegistryModel :one
+INSERT INTO models (model_id, name, llm_provider_id, type, config)
+VALUES (sqlc.arg(model_id), sqlc.arg(name), sqlc.arg(llm_provider_id), sqlc.arg(type), sqlc.arg(config))
+ON CONFLICT (llm_provider_id, model_id) DO UPDATE SET
+  name = EXCLUDED.name,
+  type = EXCLUDED.type,
+  config = EXCLUDED.config,
+  updated_at = now()
+RETURNING *;
+
+-- name: ListEnabledModels :many
+SELECT m.*
+FROM models m
+JOIN llm_providers p ON m.llm_provider_id = p.id
+WHERE p.enable = true
+ORDER BY m.created_at DESC;
+
+-- name: ListEnabledModelsByType :many
+SELECT m.*
+FROM models m
+JOIN llm_providers p ON m.llm_provider_id = p.id
+WHERE p.enable = true
+  AND m.type = sqlc.arg(type)
+ORDER BY m.created_at DESC;
+
+-- name: ListEnabledModelsByProviderClientType :many
+SELECT m.*
+FROM models m
+JOIN llm_providers p ON m.llm_provider_id = p.id
+WHERE p.enable = true
+  AND p.client_type = sqlc.arg(client_type)
+ORDER BY m.created_at DESC;
+
 -- name: CreateModelVariant :one
 INSERT INTO model_variants (model_uuid, variant_id, weight, metadata)
 VALUES (