Remove Programs tab and all supporting code

The Programs feature is superseded by Shows, which provides a more
flexible model with schedule slots. This commit removes all Programs
code across frontend and backend:

Frontend:
- Delete admin-program-form component (ts/html/scss)
- Delete program.service.ts and program.ts interface
- Remove Programs tab, form modal, and all CRUD logic from admin
  component (ts + html)

Backend:
- Delete programs API router
- Remove Program ORM model and ProgramCreate/Update/Response schemas
- Remove programs router registration from main.py
- Remove Program from seed data, seed helpers, and truncate/reset

backend/app/schemas.py

@@ -4,7 +4,7 @@ from typing import Optional
 from pydantic import BaseModel, computed_field, field_validator
 
 
-# ── Program ──────────────────────────────────────────────
+# ── Shared ───────────────────────────────────────────────
 
 DAY_NAMES = {
     1: "Monday",
@@ -17,40 +17,6 @@ DAY_NAMES = {
 }
 
 
-class ProgramCreate(BaseModel):
-    day_of_week: int
-    day_label: str
-    time: str
-    title: str
-    host: str
-    genre: str
-
-
-class ProgramUpdate(BaseModel):
-    day_of_week: Optional[int] = None
-    day_label: Optional[str] = None
-    time: Optional[str] = None
-    title: Optional[str] = None
-    host: Optional[str] = None
-    genre: Optional[str] = None
-
-
-class ProgramResponse(BaseModel):
-    id: int
-    day_of_week: int
-    time: str
-    title: str
-    host: str
-    genre: str
-
-    @computed_field
-    @property
-    def day_label(self) -> str:
-        return DAY_NAMES.get(self.day_of_week, "Unknown")
-
-    model_config = {"from_attributes": True}
-
-
 # ── Event ────────────────────────────────────────────────
 
 class EventCreate(BaseModel):