refactor: fix all P0/P1/P2 bugs and architecture issues

Bug fixes (from bugs/ directory):

- Fix cross-module DB queries in 9 modules (homework, grades, parent, diagnostic, elective, proctoring, notifications, scheduling, classes) by routing through data-access functions

- Fix shared/lib <-> auth circular dependency via new session.ts module

- Fix divide-by-zero guard in grades data-access

- Fix audit export data truncation (paginated fetch for full datasets)

- Fix missing transactions in homework grading and elective lottery

- Fix missing revalidatePath in course-plans actions

- Fix frontend permission checks using requirePermission instead of requireAuth

- Fix dashboard role routing using session.user.roles

- Fix student auth pattern (migrate getDemoStudentUser to users module)

- Fix ActionState return type handling in components

Code quality fixes:

- Remove 60+ as type assertions (replace with type guards)

- Remove non-null assertions (use optional chaining or explicit checks)

- Convert dynamic imports to static imports (grades, diagnostic)

- Add React.cache() wrapping for read functions

- Parallelize independent queries with Promise.all

- Add explicit return types to 30+ arrow functions

- Replace any with unknown + type guards

- Fix import type for type-only imports

- Add Zod validation schemas for classes and diagnostic modules

- Extract duplicate code (normalizeRoleName, normalizeBcryptHash, logger IP extraction)

- Add console.error to silent catch blocks

- Fix permission naming consistency (exam:proctor_read -> exam:proctor:read)

Architecture doc sync:

- Update 004_architecture_impact_map.md and 005_architecture_data.json

- Update management-modules-audit.md for P0-7 cross-module fix

Moved deleted proctoring event route to deletes/ folder.

src/modules/textbooks/data-access.ts

@@ -30,25 +30,37 @@ const sortChapters = (a: Chapter, b: Chapter) => {
 }
 
 const buildChapterTree = (rows: Chapter[]): Chapter[] => {
-  const byId = new Map<string, Chapter & { children: Chapter[] }>()
+  type ChapterNode = Chapter & { children: ChapterNode[] }
+
+  const isChapterNode = (n: Chapter): n is ChapterNode =>
+    Array.isArray(n.children)
+
+  const byId = new Map<string, ChapterNode>()
   for (const ch of rows) {
     byId.set(ch.id, { ...ch, children: [] })
   }
 
-  const roots: Array<Chapter & { children: Chapter[] }> = []
+  const roots: ChapterNode[] = []
   for (const ch of byId.values()) {
     const pid = ch.parentId
-    if (pid && byId.has(pid)) {
-      byId.get(pid)!.children.push(ch)
+    if (pid) {
+      const parent = byId.get(pid)
+      if (parent) {
+        parent.children.push(ch)
+      } else {
+        roots.push(ch)
+      }
     } else {
       roots.push(ch)
     }
   }
 
-  const sortRecursive = (nodes: Array<Chapter & { children: Chapter[] }>) => {
+  const sortRecursive = (nodes: ChapterNode[]) => {
     nodes.sort(sortChapters)
     for (const n of nodes) {
-      sortRecursive(n.children as Array<Chapter & { children: Chapter[] }>)
+      if (isChapterNode(n)) {
+        sortRecursive(n.children)
+      }
     }
   }
 
@@ -62,14 +74,13 @@ export const getTextbooks = cache(async (query?: string, subject?: string, grade
   const q = query?.trim()
   if (q) {
     const needle = `%${q}%`
-    conditions.push(
-      or(
-        like(textbooks.title, needle),
-        like(textbooks.subject, needle),
-        like(textbooks.grade, needle),
-        like(textbooks.publisher, needle)
-      )!
+    const nameCond = or(
+      like(textbooks.title, needle),
+      like(textbooks.subject, needle),
+      like(textbooks.grade, needle),
+      like(textbooks.publisher, needle)
     )
+    if (nameCond) conditions.push(nameCond)
   }
 
   const s = subject?.trim()