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/summarize.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"strings"
 
-	"github.com/google/uuid"
 	"github.com/modelcontextprotocol/go-sdk/mcp"
 
 	"git.warky.dev/wdevs/amcs/internal/ai"
@@ -49,9 +48,9 @@ func (t *SummarizeTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in
 	count := 0
 
 	if query != "" {
-		var projectID *uuid.UUID
+		var projectID *int64
 		if project != nil {
-			projectID = &project.ID
+			projectID = &project.NumericID
 		}
 		results, err := semanticSearch(ctx, t.store, t.embeddings, t.search, query, limit, t.search.DefaultThreshold, projectID, nil)
 		if err != nil {
@@ -62,9 +61,9 @@ func (t *SummarizeTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in
 		}
 		count = len(results)
 	} else {
-		var projectID *uuid.UUID
+		var projectID *int64
 		if project != nil {
-			projectID = &project.ID
+			projectID = &project.NumericID
 		}
 		thoughts, err := t.store.RecentThoughts(ctx, projectID, limit, in.Days)
 		if err != nil {
@@ -83,7 +82,7 @@ func (t *SummarizeTool) Handle(ctx context.Context, req *mcp.CallToolRequest, in
 		return nil, SummarizeOutput{}, err
 	}
 	if project != nil {
-		_ = t.store.TouchProject(ctx, project.ID)
+		_ = t.store.TouchProject(ctx, project.NumericID)
 	}
 
 	return nil, SummarizeOutput{Summary: summary, Count: count}, nil