feat: add Convex project backend with generic storage and org-scoped authz

Schema:
- Cut projects table to {organizationId, name, description, createdAt, updatedAt}
- Add projectSources table with git source metadata and normalized URL index
- Add projectContextDocuments table with six canonical kinds, origin, revision
- Add by_organizationId index for project enumeration
- Remove all GitHub-specific fields (ownerId, provider, repoOwner, etc.)

Backend:
- Add requireCurrentOrganization and requireProjectMember authz helpers
- Migrate signals.ts authorizeProject to organizationId invariant check
- Update artifactModel: 8 operational artifacts (removed project/business/design.md)
- Add projectStore.ts with query/mutation/action store adapters
- Rewrite projects.ts to thin generic application calls
- Update projectIssues/projectArtifacts to use requireProjectMember
- Update projectEvents.test.ts and signals.test.ts for new project creation

All 33 backend tests pass.

packages/backend/convex/schema.ts

@@ -63,25 +63,57 @@ export default defineSchema({
     .index("by_daemonId_and_createdAt", ["daemonId", "createdAt"])
     .index("by_commandId_and_createdAt", ["commandId", "createdAt"]),
   projects: defineTable({
-    ownerId: v.string(),
-    provider: v.literal("github"),
-    providerRepoId: v.number(),
+    organizationId: v.id("organizations"),
     name: v.string(),
     description: v.optional(v.string()),
-    repoOwner: v.string(),
-    repoName: v.string(),
-    repoUrl: v.string(),
-    defaultBranch: v.string(),
+    createdAt: v.number(),
+    updatedAt: v.number(),
+  }).index("by_organization_and_createdAt", ["organizationId", "createdAt"]),
+  projectSources: defineTable({
+    organizationId: v.id("organizations"),
+    projectId: v.id("projects"),
+    kind: v.literal("git"),
+    url: v.string(),
+    normalizedUrl: v.string(),
+    host: v.string(),
+    repositoryPath: v.string(),
+    defaultBranch: v.optional(v.string()),
     createdAt: v.number(),
     updatedAt: v.number(),
   })
-    .index("by_owner_and_createdAt", ["ownerId", "createdAt"])
-    .index("by_owner_and_repository", [
-      "ownerId",
-      "provider",
-      "repoOwner",
-      "repoName",
-    ]),
+    .index("by_project", ["projectId"])
+    .index("by_organization_and_normalizedUrl", [
+      "organizationId",
+      "normalizedUrl",
+    ])
+    .index("by_organization_and_createdAt", ["organizationId", "createdAt"]),
+  projectContextDocuments: defineTable({
+    organizationId: v.id("organizations"),
+    projectId: v.id("projects"),
+    kind: v.union(
+      v.literal("readme"),
+      v.literal("agents"),
+      v.literal("product"),
+      v.literal("business"),
+      v.literal("design"),
+      v.literal("tech")
+    ),
+    path: v.string(),
+    content: v.string(),
+    revision: v.number(),
+    origin: v.union(
+      v.literal("repository"),
+      v.literal("paste"),
+      v.literal("upload"),
+      v.literal("public-url")
+    ),
+    sourceUrl: v.optional(v.string()),
+    createdAt: v.number(),
+    updatedAt: v.number(),
+  })
+    .index("by_project", ["projectId"])
+    .index("by_project_and_kind", ["projectId", "kind"])
+    .index("by_project_and_path", ["projectId", "path"]),
   projectArtifacts: defineTable({
     projectId: v.id("projects"),
     path: v.string(),
@@ -165,6 +197,7 @@ export default defineSchema({
     createdAt: v.number(),
   })
     .index("by_userId", ["userId"])
+    .index("by_organizationId", ["organizationId"])
     .index("by_organizationId_and_userId", ["organizationId", "userId"]),
 
   // -----------------------------------------------------------------