feat: add image generation model and generate_image agent tool

Bots can now be configured with an image generation model (must have
image-output compatibility). When set, the agent exposes a generate_image
tool that calls the model via Twilight AI SDK, saves the result to the
bot container filesystem, and returns the file path.

- Add image_model_id column to bots table (migration 0053)
- Update settings SQL queries, service, and types
- New ImageGenProvider tool provider in internal/agent/tools/
- Wire provider in both cmd/agent and cmd/memoh entry points
- Add image model selector to frontend bot settings with compat filtering
- Regenerate swagger, SDK types, and sqlc code

cmd/agent/main.go

@@ -647,6 +647,7 @@ func provideToolProviders(log *slog.Logger, cfg config.Config, channelManager *c
 		agenttools.NewSkillProvider(log),
 		agenttools.NewBrowserProvider(log, settingsService, browserContextService, manager, cfg.BrowserGateway),
 		agenttools.NewTTSProvider(log, settingsService, ttsService, channelManager, registry),
+		agenttools.NewImageGenProvider(log, settingsService, modelsService, queries, manager, config.DefaultDataMount),
 		agenttools.NewFederationProvider(log, fedSource),
 		agenttools.NewHistoryProvider(log, sessionService, queries),
 	}

cmd/memoh/serve.go

@@ -547,6 +547,7 @@ func provideToolProviders(log *slog.Logger, cfg config.Config, channelManager *c
 		agenttools.NewSkillProvider(log),
 		agenttools.NewBrowserProvider(log, settingsService, browserContextService, manager, cfg.BrowserGateway),
 		agenttools.NewTTSProvider(log, settingsService, ttsService, channelManager, registry),
+		agenttools.NewImageGenProvider(log, settingsService, modelsService, queries, manager, config.DefaultDataMount),
 		agenttools.NewFederationProvider(log, fedSource),
 		agenttools.NewHistoryProvider(log, sessionService, queries),
 	}