refactor(store,tools): migrate IDs from UUID to bigserial int64

All internal entity lookups now use bigserial primary keys (int64) while
GUIDs are retained for external/public identification. Updated store
functions (TouchProject, UpdateThoughtMetadata, AddThoughtAttachment) to
query by id instead of guid, added GetThoughtByID, changed semanticSearch
and all tool helpers to use *int64 project IDs, and updated retry/backfill
workers to use int64 thought IDs throughout.

internal/tools/recall.go

@@ -5,7 +5,6 @@ import (
 	"fmt"
 	"strings"
 
-	"github.com/google/uuid"
 	"github.com/modelcontextprotocol/go-sdk/mcp"
 
 	"git.warky.dev/wdevs/amcs/internal/ai"
@@ -49,9 +48,9 @@ func (t *RecallTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in Re
 
 	limit := normalizeLimit(in.Limit, t.search)
 
-	var projectID *uuid.UUID
+	var projectID *int64
 	if project != nil {
-		projectID = &project.ID
+		projectID = &project.NumericID
 	}
 
 	semantic, err := semanticSearch(ctx, t.store, t.embeddings, t.search, query, limit, t.search.DefaultThreshold, projectID, nil)
@@ -66,7 +65,7 @@ func (t *RecallTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in Re
 	items := make([]ContextItem, 0, limit*2)
 	seen := map[string]struct{}{}
 	for _, result := range semantic {
-		key := result.ID.String()
+		key := fmt.Sprint(result.ID)
 		seen[key] = struct{}{}
 		items = append(items, ContextItem{
 			ID:         key,
@@ -77,7 +76,7 @@ func (t *RecallTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in Re
 		})
 	}
 	for _, thought := range recent {
-		key := thought.ID.String()
+		key := fmt.Sprint(thought.ID)
 		if _, ok := seen[key]; ok {
 			continue
 		}
@@ -97,7 +96,7 @@ func (t *RecallTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in Re
 	header := "Recalled context"
 	if project != nil {
 		header = fmt.Sprintf("Recalled context for %s", project.Name)
-		_ = t.store.TouchProject(ctx, project.ID)
+		_ = t.store.TouchProject(ctx, project.NumericID)
 	}
 
 	return nil, RecallOutput{