feat: add SpamShield router for spam detection and call analysis

- Create tRPC router with checkNumber, classifySMS, classifyCall endpoints
- Add protected procedures for rule CRUD, feedback submission, and stats
- Implement service layer with phone number normalization and audit logging
- Add ML engine with BERT stub, feature extraction, and rule engine
- Implement reputation API module with circuit breaker and caching
- Write comprehensive tests (34 tests) for all layers
- Wire spamshield router into app root router

web/src/server/api/schemas/spamshield.ts

@@ -0,0 +1,36 @@
+import { object, string, minLength, optional, number, boolean as vBoolean, picklist } from "valibot";
+
+export const CheckNumberSchema = object({
+  phoneNumber: string([minLength(1)]),
+});
+
+export const ClassifySMSSchema = object({
+  text: string([minLength(1)]),
+});
+
+export const ClassifyCallSchema = object({
+  callerNumber: string([minLength(1)]),
+  duration: optional(number()),
+  timeOfDay: optional(number()),
+});
+
+export const CreateRuleSchema = object({
+  ruleType: picklist(["phoneNumber", "areaCode", "prefix", "pattern", "reputation"]),
+  pattern: string([minLength(1)]),
+  action: picklist(["block", "flag", "allow", "challenge"]),
+  priority: optional(number(), 0),
+});
+
+export const DeleteRuleSchema = object({
+  ruleId: string([minLength(1)]),
+});
+
+export const FeedbackSchema = object({
+  phoneNumber: string([minLength(1)]),
+  isSpam: vBoolean(),
+  feedbackType: picklist(["initial_detection", "user_confirmation", "user_rejection", "auto_learned"]),
+});
+
+export const StatsFilterSchema = object({
+  period: optional(picklist(["day", "week", "month", "year"]), "month"),
+});