refactor: content-addressed assets, cross-channel multimodal, infra simplification (#63)

* refactor(attachment): multimodal attachment refactor with snapshot schema and storage layer

- Add snapshot schema migration (0008) and update init/versions/snapshots
- Add internal/attachment and internal/channel normalize for unified attachment handling
- Move containerfs provider from internal/media to internal/storage
- Update agent types, channel adapters (Telegram/Feishu), inbound and handlers
- Add containerd snapshot lineage and local_channel tests
- Regenerate sqlc, swagger and SDK

* refactor(media): content-addressed asset system with unified naming

- Replace asset_id foreign key with content_hash as sole identifier
  for bot_history_message_assets (pure soft-link model)
- Remove mime, size_bytes, storage_key from DB; derive at read time
  via media.Resolve from actual storage
- Merge migrations 0008/0009 into single 0008; keep 0001 as canonical schema
- Add Docker initdb script for deterministic migration execution order
- Fix cross-channel real-time image display (Telegram → WebUI SSE)
- Fix message disappearing on refresh (null assets fallback)
- Fix file icon instead of image preview (mime derivation from storage)
- Unify AssetID → ContentHash naming across Go, Agent, and Frontend
- Change storage key prefix from 4-char to 2-char for directory sharding
- Add server-entrypoint.sh for Docker deployment migration handling

* refactor(infra): embedded migrations, Docker simplification, and config consolidation

- Embed SQL migrations into Go binary, removing shell-based migration scripts
- Consolidate config files into conf/ directory (app.example.toml, app.docker.toml, app.dev.toml)
- Simplify Docker setup: remove initdb.d scripts, streamline nginx config and entrypoint
- Remove legacy CLI, feishu-echo commands, and obsolete incremental migration files
- Update install script and docs to require sudo for one-click install
- Add mise tasks for dev environment orchestration

* chore: recover migrations

---------

Co-authored-by: Acbox <acbox0328@gmail.com>

internal/db/utils.go

@@ -9,8 +9,22 @@ import (
 	"github.com/google/uuid"
 	"github.com/jackc/pgx/v5/pgconn"
 	"github.com/jackc/pgx/v5/pgtype"
+	"github.com/memohai/memoh/internal/config"
 )
 
+// DSN builds a PostgreSQL connection string from config.
+func DSN(cfg config.PostgresConfig) string {
+	return fmt.Sprintf(
+		"postgres://%s:%s@%s:%d/%s?sslmode=%s",
+		cfg.User,
+		cfg.Password,
+		cfg.Host,
+		cfg.Port,
+		cfg.Database,
+		cfg.SSLMode,
+	)
+}
+
 // ParseUUID converts a string UUID to pgtype.UUID.
 func ParseUUID(id string) (pgtype.UUID, error) {
 	parsed, err := uuid.Parse(strings.TrimSpace(id))