Per-project access control + UI/feedback/admin refinements

Access control:
- project_members table; non-admins only see/operate on assigned
  projects (enforced across projects, SOPs, work packages — 403 else),
  admins bypass. Creating a project auto-grants its creator access.
- Admin API to get/set a user's project assignments, plus a checkbox
  assignment dialog in the Admin Console user list.

UI / workflow:
- Login page: drop the "Prime Controls" wordmark next to the logo.
- SOP tool: remove emoji icons from buttons and nav tabs.
- Rename "Step Comments" to "Feedback"; the author auto-populates
  (read-only) from the signed-in user.
- Move usage-log viewing to the Admin Console; add an admin card that
  lists all feedback/comments (who, what, page + step, when).
- Sample project name -> "Micron FMCS Install (sample)".

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

server/models.py

@@ -12,7 +12,7 @@ can upsert without round-tripping a sequence.
 """
 from datetime import datetime, timezone
 from typing import Optional
-from sqlalchemy import String, Boolean, Integer, DateTime, ForeignKey, Text, JSON
+from sqlalchemy import String, Boolean, Integer, DateTime, ForeignKey, Text, JSON, UniqueConstraint
 from sqlalchemy.orm import Mapped, mapped_column
 from .db import Base
 
@@ -137,6 +137,23 @@ class User(Base):
         }
 
 
+class ProjectMember(Base):
+    """Which users may access which projects. A user sees/operates on a project
+    only if a row links them to it (admins bypass this entirely). One row per
+    (user, project) pair."""
+    __tablename__ = "project_members"
+    __table_args__ = (UniqueConstraint("user_id", "project_id", name="uq_project_member"),)
+
+    id: Mapped[str] = mapped_column(String(40), primary_key=True)
+    user_id: Mapped[str] = mapped_column(
+        String(40), ForeignKey("users.id", ondelete="CASCADE"), index=True
+    )
+    project_id: Mapped[str] = mapped_column(
+        String(40), ForeignKey("projects.id", ondelete="CASCADE"), index=True
+    )
+    created_at: Mapped[datetime] = mapped_column(DateTime(timezone=True), default=utcnow)
+
+
 class Comment(Base):
     __tablename__ = "comments"